Sharon Rooney, the star of My Mad Fat Diary, talks about the third and final series...

When we left Rae at the end of Series 2, things were looking up. Presumably it's not all going to be plain sailing from here on in?

Well, it never is. But I think it's a nice mix. That's the best thing about My Mad Fat Diary - it's real. I think everyone's expecting a real doom-and-gloom series, that's what I keep getting on Twitter: "Is it going to be really sad?" "Am I going to be really upset?" Come on. It's still set in the 90s. There's still some great music out there. She's still got a great group of friends. There will be fun, too.

She's a big sister now. Is that going to change her?

That's a good question. I don't know. I think it's definitely brought her and her mum closer. But I didn't really have a lot to do with Baby Bouchtat.

There's a new character in Rae's life, Katie Springer. What can you tell us about her?

Yes. Rae meets her when she has her interview at Bristol. Rae kind of knew who she was - she was the year above Rae, she didn't hang out with her, she doesn't really know her that well, and she's suddenly come into Rae's life, and she shakes things up a bit, I guess, and gives Rae a lot more things to think about.

Katie is played by Faye Marsay, who's been in everything from Fresh Meat to The White Queen to Game Of Thrones. What was it like working with her?

It was an absolute joy working with Faye. I always think it must be hard for people to come into such a close-knit group, because we only had Turlough [Convery, who plays Liam] come in last year, the rest of us have been together from the start. But both Turlough and Faye did the same thing, they just slotted right in, and it was as if they'd been there the whole time. She's so incredible, so real. When we had our first scenes together, I didn't even realise she was acting, she was so natural. I thought she was just chatting, until I realised we were actually filming.

Where is Rae at the start of Series 3, in terms of her mental health? She's in a better place than she's been in the past, isn't she?

Yeah, definitely. When we come back, it's a year on, and she's in a really good place. She hasn't hurt herself in a long time, she's feeling really good about herself. So when we first see her in this series, she's doing really well.

The series deals with some difficult and emotional themes, but fundamentally it's a story of hope, isn't it?

Yeah, I think what it does is deal with things in a real way, that lets people who are going through those things, or who have gone through those things, see the truth. That's why I love this show. Some things are really difficult, but you always know that it'll help someone. There's no sugar-coating anything in this, it's very raw, but it's also optimistic. This series, in particular, I think is very raw.

Rae means an awful lot to people. Can you please talk a bit about the communication you've received from fans over the years...

It's quite overwhelming, actually. I finished the vlogs last week, and I found it quite emotional signing off. When you're making telly, you kind of forget, because you're so busy, that actually other people love Rae as much as I do. I don't think anyone could love her more than me, but it's certainly on a par. That's just overwhelming.

The tweets - I've had a lot today, from people who have watched the vlog, and they've been so kind, thanking me and so on. To hear that people have gone and got help, or are thinking of going and getting help, is all I ever really wanted from playing this character. So it's really overwhelming. It's nice when people say that they don't feel alone. That's kind of amazing.

You've often said you hoped the show would help one person. It's done a lot more than that, hasn't it?

Yeah. It's a huge thing, and it's a lovely thing to know. Even when you're knackered, and you're finding things hard, to know that it's going to make a difference is huge. It's such a lovely, lovely feeling.

Aside from letters and tweets, have you had people come up to you and talk to you in the flesh?

Yeah, so many people. And people always assume it's teenage girls, and it's not. Sometimes it's older people, men and women from all different walks of life. That's really nice. Sometimes it's nice when you get a mum come up to you and say "I didn't know how to speak to my kid, I didn't know how to approach the issues, and after watching My Mad Fat Diary and seeing how your mum dealt with things, even if it wasn't the best way to be, we've managed to sort things out."

Speaking of your on-screen mum, Claire Rushbrook, you formed a real bond with her, didn't you?

Oh, such a good bond. This was my first TV job, and I'm a huge fan of hers anyway, so when I found out she was playing my mum I was beside myself. She took me under her wing, and taught me so, so many things that you can't learn anywhere else. She's been such a fantastic friend, I've definitely made a friend for life.

Has Ian Hart (who plays Kester) made as big an impression?

He's so fantastic. The scenes with him, I just treasure them. He just makes you feel so safe and so secure, in the same way that Claire did. This was the first time I'd worked with people of their standing, and it felt like a big thing, but they never, ever made me feel like I wasn't on a par with them. They always made it a collaboration, and gave me a chance.

The scenes with Kester are amazing, especially this season - there's a lot going on between us. It was so sacred, really. When we finished, I found it really hard, saying goodbye to Ian. That was one of the hardest goodbyes of all.

Was that because of the intensity of the scenes you'd always filmed together?

Definitely. Although you're acting, you are totally laid bare in those types of scene, and there's nowhere to hide, it's just the two of you. So you see each other in a way that you don't always get to see other people. It was so, so special, we have a real bond.

Is there a similar feeling with "the gang"?

We're kind of like "the gang". We all have our own little roles. I kind of feel like we've all grown up together. It's so nice to see how well they're all doing. We're all really supportive of each other. It's really nice, because often people say stuff like that and then never see each other again, but I promise you that we are all really close.

It looked like it on the vlog...

I had so much footage, you would not believe it. Most of it was just us messing around.

Of all of the gang, who is the most like their character, and who is the least like them?

I think Ciara [Baxendale] is very like Izzy. She's the sweetest girl, and is prone to saying the most random thing. She's also got a really good sense of style, like Izzy, she always looks really cool. Who's least like their character? That's a good question. Jodie is nowhere near as bitchy as Chloe is sometimes, but she is definitely as funny as Chloe. There are a couple of moments in Series 3 where she does these tiny, subtle things that are hilarious.

Have you had moments during filming where corpsing has been a real problem?

Yeah. The worst, worst days for that are pub days. For some reason, when we all get together and we're all in that pub, it's like a weird mist falls over us all, and we just can't stop talking, putting pictures on Instagram, and just completely misbehaving. It's awful. Me, Jodie and Dan, the three of us together is a nightmare. We just make each other laugh. We gave Dan a really hard time this season, just winding him up with every line he said. It's always hard for the crew, who want to get on, but we're having a ball!

We've talked about what Rae means to other people. What does she mean to you?

I think, for me, it was such a baptism of fire. You're given this character, who is funny and clever and brilliant - there are a lot of ways in which I wish I was more like Rae. But Rae wouldn't think she was cool or interesting or clever, especially in Series 1. I kind of feel like I've grown up a bit with her. We've gone through things together - filming this has seen me moving away from home, finding a new group of friends, just as Rae did.

She will always have a huge, huge part of my heart, I don't think I'll ever play anyone like her again. It's just been a joy to play her. Some days have been a nightmare, but for the most part it's been such a special journey, and I'm really going to miss putting on those silver hoops and the Converse.

What have you learned from playing Rae, and the people that has brought you into contact with?

I think I've learned - and it's a Kester line - that if people don't like me, they can f*** off. That sounds a bit vulgar, but it's so true. A lot of the time, especially as an actor, you're striving to make everyone like you all the time, and to be good enough all the time. And actually, this has brought me that peace within me to say "You know what, if they don't like me or what I've done... oh well. I'm good enough as who I am, and I don't have to change to suit someone else's idea of perfection."

How has My Mad Fat Diary changed your life?

It's changed it hugely. It's given me so many opportunities, professionally and personally. It's been a huge challenge, it's not all been plain sailing, but I think it's made me a better person.

What did you do after you filmed your final scene?

I had a sob, a massive cry, and then I was given some amazing gifts from the crew, and then I had to go home and pack, because I started a new job two days later, which I've been working on ever since. So I haven't had a chance to grieve properly that it's over.

'My Mad Fat Diary' returns on Monday 22nd June at 10pm on E4.