SOLVED. 2000s children/ YA book about a girl who ends up in an alternate future with an older version of herself - Frankie something? [s]

[Ellen]

I read this book in the 2000s so it must've been published at least that far back or potentially older.

I remember very vaguely that the plot involved a girl (around 10 or so) being transported to an alternate future somehow where the old(?) man is revealed to be evil. She then somehow gets back to the correct timeline.

One of the elements which revealed she was in an alternate universe was her name/ her friend's name change being revealed as Frankie from Francesca/Frances. There was also something about a car park discussion but I don't remember what about!

Any ideas are very welcome, thank you!

[Becca]

It could be Thief! by Malorie Blackman. The main character Lydia's best friend is called Frankie (a nickname for Frances) but in the alternate future, she calls herself Fran instead.

[Ellen]

Thank you!!