Science Fiction on girl who can stop and start time verbally (by yelling "stop" for time to stop)

I remember I read this story a couple years ago, but I forgot the title of it. I'm pretty sure the book's audience is teenagers or older children. It was about this girl who found out that she could stop time (for everyone else) by yelling "STOP!" and that everyone who shared her birthday (date) still had time unfrozen for themselves. She might have had a brother, but I'm not sure. There was a phrase that she used to make time continue again, but (again), I forgot. One detail that I remember is that while walking through a frozen city, she notices a pair of young ballerinas and conjectures that everyone who shares her birthday is unaffected by the freezing of time. But I read this book so long ago, so some details might be messed up.
Thanks!

Did you find the book? I've been looking for the same one.

>1 embirdie: I'm pretty sure this is Switch or at least part of that series.

Thank you so much!

>4 PiperGrounds: You're welcome!