I read this in hardcover close to when it was released, I think. This book numbers among a few dozen from my tween years that have stuck with me. I was 12ish, 13ish on an Air Force Base in South Dakota. I was going through puberty, and it was awful. But the children's/YA librarian at the base library was a GODDESS. I don't know who she was but I owe her everything. The section was beefy and robust and full of novels beyond Babysitter's Club and R.L. Stine.
I've not been able to find this book as an adult to see if it's as good as I remember, but it had all the elements I liked then: fab heroine, a hint of romance, some swears, lots of snark. (I still remember the bit where our heroine is trying to get First Aid, but her French is so bad she only manages le premiere aide or something like that. It tickled me so.) Oh, and a French setting, which I'm still a sucker for.
Other than the time travel, and the first aid quip, I don't recall much else about this book, other than deep, intense affection. What more can I ask for?