Rae is your first major TV role, what were you doing before?

My best friend Anna Devitt is a stand-up comedian. Before I got Mad Fat, I was doing Theatre And Education (TAE) tours [travelling the country performing educational skits to school children] when she said, “Why don’t you come and do stand-up with me?” I turned up for the first gig completely unprepared. I thought I’d just stand there and sing a comedy song. I did I’m Not Pregnant, I’m Just Fat, but gave it a ‘Scottish twist’. Luckily, I think people felt a bit sorry for me. When I came off stage people patted me on the back and said, “Well done. Very brave.” I knew then it wasn’t good. But after that we actually toured together, doing female comedy shows at The Fringe and at Henley. It was great.

How did My Mad Fat Diary come about?

Totally by accident. I was on tour and I was feeling a bit sorry for myself. Auditions weren’t going well and I’d convinced myself I was going to quit acting completely. Then my agent rang and said, “Can you be in London tomorrow?” I wasn’t having any of it. But he sent me the script anyway. I read the first page and went, “I’ll be there.”

What was the audition like?

I just thought, ‘I’ll make them laugh.’ I didn’t want to show them anything vulnerable. But at my last audition I found out a friend had passed away just before I went in. The last time I had spoken to her she said, “Do not come home without this job.” When I heard she’d died, I thought, ‘I can either fight for this, or I can go home. But if I do go home, she still won’t be there, so why not honour what she said.’ That’s when I realised that I needed to stop being silly and stop thinking that I could get through life just by making people laugh. That it’s fine to not be fine. It’s OK to say, “Look, something really bad’s just happened. But I’m here and I still want to do this.” I think that really changed me as a person.

What were you like as a teenager?

I kind of hung around with everybody. I wasn’t a threat to the gorgeous girls, and the boys didn’t see me in that way either. I tried to be one of the cool ones and get into certain music – and had an attempt at a goth phase – but it never really worked. I always looked a bit try-hard. I didn’t get up to anything naughty. I look back now and think, ‘I wish I’d been a bit worse.’

Did you have quite a theatrical upbringing?

My dad has thousands of CDs. He actually used to DJ at my school discos – HORRIFIC, that was why I was not popular at school. Both my parents love the theatre and on my 16th birthday they surprised me with a trip to the West End where we went to see Fame and Saturday Night Fever. I was just in awe.

Girl meets world: Sharon Rooney