The musical theatre star is one of the biggest names in the business, one of the first to be called by casting agents when booking shows such as Queen's We Will Rock You and now classy Rod Stewart showcase musical, Tonight's The Night.
However, while musical theatre performers of today are nursed through stage school and then hot-housed in drama colleges, the lady from Clydebank reveals a different development experience.
"I'm not trained at all," says the blonde singer, just minutes after appearing on stage with the Rod Stewart musical in Manchester.
"My early experience as a singer was the working men's clubs in Glasgow. My dad was a sound man, so from the age of 12 I've been working the circuit.
"I also did the talent competitions in pubs such as the likes of Ivory Black's, which I won, going up against the adults."
The working men's clubs world of lager and bingo was far from auspicious. But there's no doubt it helped create character.
"I remember the time when I was 14 and appearing at a miner's club. And there I was singing Over The Rainbow, all wistful and wonderful, and this bloke stood up in front of me, looked at his drinking pal and yelled, 'Right! Do you want a pint or 'no?' And I had to carry on singing 'Someday I wish upon a star. . .' But what this taught me was to stay in the moment. And it was great training that's never left me."
Jenna's ability to remain in the moment was called upon just the previous night on stage.
"It really was," she says, grinning. "I was on stage singing I Don't Want to Talk About it, (a poignant, hairs standing on the back of the neck moment) when a guy got caught up in the song so much he lost it a little and shouted out 'Fan - tastic!'
"I had to ignore him completely and concentrate on delivering the lyrics.
"In this line of work, I'm used to interruptions. I've actually had to endure people calling taxis while I'm on stage singing."
Jenna's voice is natural with an awesome range, but what sets her apart on stage is she can be hypnotic and powerful. She can sing soft ballads and powerful rock anthems.
"I have always loved singing and performing. I'd go with my gran to old people's homes when I was a wee girl, and sing, and I did amateur dramatics in Glasgow.
THE only training I had of any kind was attending Saturday afternoon sessions as a kid with Dorothy Paul."
Jenna was with the stage legend for six months, on Saturday afternoons.
"Performance however was everything to me. But it's ironic because when I went to see my school careers adviser and said I wanted to be a singer and actress she laughed at me."
Jenna's dad was circumspect about his daughter's desire to become an entertainer. He reckoned his daughter should be an accountant.
"I got five Highers, with good grades, so he wanted to make sure I had a back-up career. But once I decided to go for performing my parents have been so supportive.
"They are forever getting on planes to see me in Sweden or wherever."
Aged 16, Jenna faced a career crossroads - go to acting college or take up a job offer. She took the job, a summer season in Scarborough with Bobby Davro's show, Rock With Laughter.
"It was great experience and I think I learned more than I would have done at college. I'm not saying college is a bad thing, but you gain so much from being in the business."
Jenna's career certainly hasn't suffered.
She appeared in We Will Rock You for five years in London, has played the Narrator in Joseph and starred in Boogie Nights with Shane Richie.
Now, she is reinventing a range of Rod songs, to incredible effect.
But isn't she a little too young (in her mid-30s) to be a Rod fan? "No, my mum and dad played Rod Stewart records all the time, and I think the songs are great.
"And when I sing I Don't Want to Talk About it, it really gets to me. It's my journey. It's about me growing up."
Jenna is hugely excited at the idea of performing in Edinburgh in two weeks' time and Glasgow this summer in a show that features 25 of Rod's greatest hits.
"The last time I appeared in Glasgow was at the King's Theatre when I was 16, in panto with Stanley Baxter.
Sadly, he didn't like kids very much. He wasn't horrid or anything. He would sign the programmes, but he didn't connect with kids.
"He was there to do his thing and didn't bother with us. He did his show, we did ours."
Jenna's love for musical theatre hasn't waned over the years.
"There is nothing like performing in a theatre. I love the tech week when the theatre is empty and all mysterious.
"Then you walk in and there's an audience. And with that comes an energy.
"And when you think about it, I get to work with my friends, sing great songs and mess around. What's not to love?"
l Tonight's The Night, the King's Theatre, June 2-14