Just the one albatross around your neck? Pah, that’s for wimps – Susan McFadden has two.

First, there’s the stigma of being a reality TV personality. Earlier this year, the blonde, apple-cheeked Dubliner won Grease is the Word, Five’s ten-week search for an eager young virgin/vamp to fill Olivia Newton-John’s spandex on the West End stage. But McFadden, 26, must also contend with the equally problematic distinction of being the little sister of the former Westlife singer Bryan.

“Yeah, I’m a sucker for punishment,” she giggles, curling her legs underneath her on a couch in a Central London hotel. She is in rehearsals for her starring role in a touring production of Seven Brides for Seven Brothers, an adaptation of the classic musical in which a brood of boys troop down from the mountains in search of housekeeping totty. It’s not hard to imagine McFadden, radiant in a blue polka-dot dress, as a wholesome home-maker with an apple pie in the oven. She also proved on Five that she has the silky voice and robust professionalism to carry a show.

But she is aware that the spectres will continue to haunt her. “You don’t want to be known as Susan McFadden, the girl from the reality TV show. You want to be known as Susan McFadden . . . ” She gropes for the words: “lead woman in a musical!” She certainly felt the strain at the beginning of her Grease run: “Everyone was lovely but I was putting the pressure on myself, thinking, I need to prove to everybody that I’m capable. You want to be respected by your peers. But after a day or two it was fine.”

The second stigma will be harder to shake off. When asked whether Bryan’s profile has counted against her, she trots off a well-rehearsed line: “No, it’s a totally different thing: he does pop and I do this. I can’t write music, but he can’t do what I do: go up on stage and act.” Bryan – who now divides his time between Ireland and Australia – doesn’t give her advice, she insists, and they don’t discuss work. But their professional careers have intersected at least once.

In 2003 she entered You’re a Star, Irish TV’s search for a singer to represent the country in the Eurovision Song Contest, performing a song written by Bryan. Although she did not get through the initial public vote, she made it on to the show following a wildcard request by one of the judges – Kerry Katona, her brother’s then wife. She was eventually eliminated anyway, and looks thoroughly embarrassed by the whole episode: “My brother was writing an entry for Eurovision and wanted me to sing it, so he made me do this thing. But I didn’t get through and it’s just as well. It made me want to move to London and move on to even better things.”

What was her take on Katona’s intervention? “I’m not going to talk about her!” she shoots, before I have finished my sentence. But it must have been considered a bit dodgy in some quarters. “I’m not even going to mention her name,” she insists, smiling through gritted teeth. “Not allowed!”

By whom? There is a stern shake of the head.

Does the stonewalling relate specifically to You’re a Star or to a more general distaste for Katona, whose erratic behaviour since splitting with Bryan has resulted in her figuring in several Most Hated and Most Unfit Mother polls? The latter, you suspect, but McFadden refuses to elaborate.

I try a change of tack. Was she ever worried that Bryan would be seen as pulling strings for her in You’re a Star? “Well, I didn’t win. It was probably a bit of both, both sides.”

It’s a good point. Bryan’s solo career hasn’t been electrifying and Susan has actually been a star in Ireland for much longer than her brother, who is three years older. Her first high-profile role came in 1994 when she played the lead in a Dublin production of Annie: “It was quite a big deal, in all the papers, which was quite strange for an 11-year-old.” Television and stage work followed, so she was a familiar, 15-year-old face in Ireland when Westlife emerged. She claims never to have been teased by her mates at school for having a namby-pamby teen pin-up for a sibling: “No one really bothered. It wasn’t a strange thing for him to do well, too; it wasn’t like, Oh God that came out of nowhere!”

They were always close as kids in Dublin, where they attended the same Billie Barry stage school. That was their mother’s idea, but McFadden showbiz world domination was never the aim, she insists: “My mum just sent us as a hobby. When we said we’d like to do this when we grew up, she was like, ‘No you won’t, you have to get your [high school] leaving certificate.’ ”

Bryan got away with murder in comparison with his kid sister: “I wasn’t allowed to do anything and felt so cheated. He was quite naughty and never got caught but I was good and when I did do something wrong I always got caught. Did she ever go out with any of Bryan’s mates? She looks aghast: “Oh, that would not be allowed!” So her father, a pharmaceutical sales rep, was protective of her? “No, my dad’s really quiet. It’s my uncle Gerald who’s the surrogate dad when it comes to the boyfriend vetting thing.”

The latest suitor to pass the Gerald test is the former Hollyoaks actor Adam Booth, who is currently appearing down the road from our interview in the Take That musical Never Forget. They have bought a flat just outside London in Kent. She is happy living in the South East, although she admits that she has fewer close chums than home in Dublin, where her parents and a horde of more than 70 cousins (her mother is one of 11 children, her father one of 14) still live.

After a year doing Grease, she is excited about Seven Brides, although the change in singing style from poppy to more traditional has been a challenge. She likes the famous 1954 Howard Keel screen version, but prefers the stage production she saw last year in the West End because it was “live-lier, more colourful”. Her own populist version may be destined for the same critical reception as Grease, which received some stinging reviews.

Did she read them? “Not really – we were told not to. The producers came on stage before the first night and said, don’t bother reading the reviews, they’re going to be crap, because the critics want to see a piece of art and Grease is cheesy pop. But the public absolutely love it, so it doesn’t matter what the reviewers say.”

Still, she has a thicker skin these days after Grease is the Word, during which she was confined to a house with her fellow contestants and had her performances scrutinised weekly by a bizarre panel including David Gest and the 1980s pop star Sinitta. The nerves took their toll. “Everyone said they could hear me before they could see me because I always had a bottle of Kalms rattling in my bag.” Kalms? “They’re pills you take to calm your nerves,” she says. “They’re only herbal!” she adds, perhaps fearing I would think she had gone the way of her former sister-in-law.

Susan stars in the brand new UK tour of Seven Brides for Seven Brothers, which plays at the Blackpool Grand Theatre until Saturday 6 September, Box Office: 01253 290 190 and then visits over thirty cities and towns including Edinburgh, Sunderland, Oxford, Bristol, Liverpool, Nottingham and Manchester. For a full list of tour dates, visit www.ukproductions.co.uk

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