WHEN Sharon Rooney was three, she knew exactly where her future lay. The Glaswegian star of My Mad Fat Diary and Two Doors Down had set her heart on one thing: becoming Ella Mint.

It all began on a visit to see the pantomime Cinderella. Sharon was up dancing in the aisles when an old lady a few seats along pointed and said: "Look at her, she's in her element …"

"I thought: 'I am. You're right. I'm Ella Mint,'" she recalls. Sharon had found her calling and in that moment a dream took flight.

A quarter of a century later and Ella, or rather Sharon, sits opposite me in a quiet corner of Hotel du Vin at One Devonshire Gardens.

The 27-year-old was catapulted from relative obscurity and into the public eye with her ground-breaking role as teenager Rae Earl in the Bafta-nominated E4 comedy drama series My Mad Fat Diary in 2013.

The show tackled issues such as mental health, suicide, body image and self-harm.

She has since built her profile in the BBC's Mountain Goats, Sherlock and Two Doors Down, the latter playing Elaine C Smith's long-suffering daughter.

There was also a part in the 2015 film Hector with Peter Mullan.

Her latest role in the forthcoming ITV drama Brief Encounters sees Sharon cast as larger-than-life hairdresser Dawn.

Alongside an unlikely band of friends, Dawn swaps a humdrum life in Sheffield circa 1982 for something a tad racier: organising Ann Summers parties.

The stellar cast includes Penelope Wilton, Sophie Rundle and Angela Griffin.

Sharon admits that when the script first arrived, she couldn't put it down.

"Dawn is one of those characters where I thought: 'Oh, I know who you are …'" she says.

"And then, as I scratched the surface, I realised there is so much more to her.

"At first you do think: 'Yep, I know your type. You're the funny and cheeky one. Got it!'

"But then you realise she is carrying a lot of heartache."

The series is a nostalgia-fest packed with electric-blue eyeliner, geometric knits, crimped hair and Princess Di-inspired high-necked blouses.

Sharon's character has a passion for neon leg warmers – the bolder, the better.

While she is too young to have embraced such eye-watering style choices first time around (Sharon was born in 1988), that doesn't mean there haven't been dalliances.

"I went through a phase at college where I wore leg warmers for a good few months," she says. "I have no idea why. I was never a wacky dresser.

"I had erased it from my memory, but then Dawn's leg warmers brought it all flooding back. Mine were black while hers are bright colours like pink or blue, and worn with every single outfit."

Today there's not a leg warmer in sight. After initially peering cautiously around the door, Sharon breezes into the room with a disarming smile and wicked sense of humour.

She has an expressive face with eyes that widen like those of an owl as she emphasises a particular point.

"I can't hide how I feel," Sharon tells me later. "It has been a pain my whole life."

Brief Encounters is about four women who ultimately become masters – mistresses – of their own destiny. I'm curious about how Sharon prepared for the role.

It's easy to forget that while these days Ann Summers has a shop on almost every UK high street, throwing parties back then was still a largely risque business.

Sharon had lunch with two women who began organising parties in the 1980s and continue to run them today.

"That was such an eye-opener," she grins. "They said it was all very hush-hush.

"You wrote down your order on a form, sealed it in an envelope and handed it to the host. Your package was then delivered wrapped in brown paper."

The big roles keep coming for Sharon. She has recently been cast in Steve Coogan's new fantasy comedy Zapped! alongside The Inbetweeners' James Buckley and Games of Thrones actor Paul Kaye.

A second series of Two Doors Down is also in the pipeline.

The biggest change since starring in My Mad Fat Diary, says Sharon, is being recognised on the street. Although some of the interactions do leave her baffled.

"I'm really approachable. I love chatting and taking photographs," she says. "Sometimes people do this thing which makes me laugh where you see them going like this …"

Sharon mimes someone attempting to take a sneaky picture with their phone. "And I think: 'What use is a photo of me picking up broccoli?' They could just say: 'Let's take a picture together.'

"Others do this weird passive-aggressive thing where they say: 'I don't even know who she is!' and I always find that funny because it's not like I'm swanning around Asda with six pugs …"

Before landing her breakthrough role in My Mad Fat Diary, Sharon had spent three years working with school-touring group Theatre in Education.

A soul-sapping cycle of unsuccessful auditions coupled with homesickness had taken their toll and she was close to quitting acting altogether.

Now she is Ella Mint – how does that feel? "Weird." Is it everything she thought it would be? "No. But things are always different than what you think they'll be like."

Sharon reveals she nailed the Lincolnshire accent for My Mad Fat Diary to such perfection that some fans refused to believe she actually hailed from Glasgow.

"People kept saying on Twitter that my Scottish accent was rubbish and why was I getting all these parts?" she says.

"After Two Doors Down, a woman came up to me. Her exact words were that my accent was 'getting there, hen …'"

As she hops into the taxi to leave, Sharon gives a mischievous grin. A young woman off on her next big adventure. One might say she's in her element.

Brief Encounters begins on STV on July 4 at 9pm. Thanks to Hotel du Vin at One Devonshire Gardens, Glasgow (hotelduvin.com)