And it’s not just because she loves the programme ... the bubbly nine-year-old Souter plays the eponymous Molly in the show, which ended its 20-episode first series just before Christmas.
The show is a bit like an urban Balamory, but the kids are the stars. And, despite Mimi’s relative inexperience in acting, her confidence shines through.
It’s all been a bit of a rollercoaster year for the Robertson household, since Mimi won the part in an open audition, and filmed the entire series during her summer holidays.
And now Mimi, who attends Selkirk’s Knowepark Primary School, is fast becoming a bit of a celebrity at school.
Her dad, 45-year-old Mark, told us: “A lot of the younger kids at the school kind of stare at her, as if to say ‘Don’t I know you from somewhere?’. The staff at the school have all been brilliant as well.”
Mimi’s real big brother, Beck, who is 12 and is a pupil at Selkirk High School, is also incredibly supportive, as is her mum, Krista, 51.
Mark added: “Mimi is certainly not massively experienced in acting at all, as this is her first main role and only her second real part.
“Her first role was a voiceover for a Danish film, Vitello, which appeared in the Edinburgh International Film Festival last year, doing her character’s translation from the original Danish.
“It was just a couple of hours’ work, but she was thrilled.
“The woman who ran these auditions suggested Mimi should audition for a part in a new pre-school kids’ drama set in Scotland.
“It was an open auction, but Mimi got the main role!”
To do so, Mimi went through three auditions, beating 1,500 other talented youngsters along the way.
The show, which is set in the fictional town of “Bridgetown” is filmed in Glasgow, and it follows the adventures of Molly and her brother Mack (played by Joshua Haynes).
Mimi’s character helps her brother on his toy and record stall, getting into silly scrapes, singing songs with the rest of the cast and smiling her infectious smile.
Mimi had got the performing bug after “doing wee bits and bobs for fun” for the Creative Stage group in Selkirk.
Mark said: “She just enjoyed it. She hasn’t been desperate to play little orphan Annie all her life or anything like that!”
He added: “She has really taken it all in her stride, and the school has been super-supportive of her.
“And, of course, with the BBC commissioning another series, it means that her summer is all set to be just as busy as it was last time round.”