Well, actually, it was sister Summer Strallen who said it, according to one of the more respectable national newspapers.
Summer was quoted as saying: 'By the time we were 18 months old, Scarly and I were going to my grandmother's dance school. Scarly was sensible and always did as she was told...'
And in the same interview, Summer spoke of the time both sisters were in Chitty Chitty Bang Bang, insisting again: 'Scarly's a lot more sensible than I am.'
In the face of such evidence, Scarlett can no longer deny it.
'Well, I'm probably the quietest one, let's put it that way,' she laughs.
'I think Summer has mellowed. She was always the more rebellious one growing up, and I was the most responsible.
'But I was just more quietly rebellious. She was more overtly having a good time, if you know what I mean...'
She leaves that one hanging in the air.
Comparisons have mostly been between these two, who have both had leading roles in major musicals, but they are part of a vast stage family.
Their parents are both dancers by training, and so are two aunts - one of them being Bonnie Langford, no less.
And following on behond Scarlett and Summer are two younger sisters, Zizi and Saskia.
Scarlett is now playing Marion, the female lead, opposite Brian Conley in The Music Man at Chichester Festival Theatre, and Zizi is also in the cast.
'Just watching her blossom and be so confident in the rehearsal room has been wonderful. When I started at 16 I was so shy. Zizi's just 17 and I'm really proud of her. I'm trying not to cramp her style.'
Zizi is the television veteran among the sisters, being cast 'in all sorts of period dramas,' says her eldest sister.
'She was tiny when she was younger, and is still very beautiful with big brown eyes.'
And Saskia? 'She has a fantastic voice and will want to do pop singing. They all want to be pop stars at that age, don't they?'
Careful, Scarlett, you are beginning to sound like a grandmother.
She laughs: 'Well Marion in The Music Man is quite grannified, so I'm just getting into character!'
In fact Scarlett will be all of 26 on Chichester's press night, next Thursday< July3>, so she is both praying and working for a happy birthday.
But at least she has been enjoying rehearsals 'fantastically', she says.
'It's very uplifting as a show and we are having a really good time.
'I didn't know the piece at all. Although I grew up watching lots of MGM films I didn't see that one. I don't know why because it's really fun with so many big numbers. I get some brilliant songs - like Till There Was You, which the Beatles covered, and Goodnight My Someone.
'We need to come through with the real human story, though, and it's quite complicated because the lead man is quite hard to like at the beginning, conning people into giving him their money.
'But Marion is gorgeous because she's not a stereotypical, soft, fey, leading girl. Lots of the characters in those musicals have a bit of feist about them but she has a good deal of it because she's very intelligent.
'She's at a crisis point in her own life when Harold Hill comes in and rocks her world and everything she believes in sort of crumbles.'
Brian Conley loves reminding Scarlett that they were in pantomime together at Wimbledon Theatre in the late 1980s when she was just a babe. Well, he would, wouldn't he?
She has since played the title role in Mary Poppins and Truly Scrumptious in Chitty Chitty Bang Bang, both in London, and Summer is now playing Maria in The Sound of Music, after taking over from TV casting show winner Connie Fisher.
Scarlett, who declares Summer's Maria 'superb', says all the family have always been very close.
'When I grew up my parents were both in shows as dancers and I grew up with that. This business does consume your life because it's your passion as well as your job, and it was hard to imagine anything else.'
But now she does to an extent see herself going in a slightly different direction.
'It's interesting being in a big family who all talk the same language, and at the same time trying to define yourself as an individual.
'But we all have our different passions. Summer is very interested in doing television and I'm very interested in doing straight plays.
'Before we started rehearsing The Music Man I did a David Mamet play in London, The Shawl, which is very rarely done.
'It's about a medium and there's a seance, and we were doing it in a very small theatre where the audience was virtually on top of you. That gave it a really eerie atmosphere, and it was so gripping, and such an amazing challenge.
'I did Poppins in an enormous proscenium-arch theatre with a 26-piece orchestra, and even when you didn't feel like it, once you heard that strike up it turned you on. 'But then in a straight play in a small theatre, people rely on you to be so focused and I loved that too, having time to take the characters apart.
'Sometimes with musicals there's so much to cover with all the routines and costumes and scenery.'
So maybe we can expect to see Scarlett in a play in Chichester's smaller auditorium, the Minerva, some time.
Well, doing something so completely different from The Music Man would be one way of casting off that 'sensible' label.
The Music Man is in repertoire at Chichester Festival Theatre until August 30.