YA Fantasy, probably early 00s, girl is able to time travel using crystals?

[Stephanie]

I don’t really remember any plot details, so this one might be impossible to solve. But I remember a scene where the girl protagonist uses a crystal to time travel forward so far that she eventually comes “back around” to the past; like goes through the end of the universe and is essentially able to travel to the past by traveling through the future. She has to use some kind of power or magical ability to use the crystals, it’s not just the crystals themselves. I believe she had two crystals, and the one that could help her travel to the past was broken, and she had to use the future crystal to get to the past. I think it may have been part of a series, but I’m not sure.

[Kris]

Stephanie, around what year did you read this book? A range of years is fine.

How old is the girl? Where does she find the crystals? (Spoilers are okay in the comments - just give us a clear warning before revealing a spoiler.)

What's her original time period and location (country, region, well-known city, small town)? Or does she live in a fantasy world?

[Stephanie]

I probably read the book between 2005-2008 if I had to guess.The girl was definitely “tween” age, 11-14ish.
I think it took place in a seemingly normal world- as in not everyone had magic powers, but the protagonist did, and I think some other people. I don’t remember much else, and definitely no specifics about locations, unfortunately.