SOLVED. YA Fantasy book about a girl who goes through a mirror into a new world. Read around 2014-2018. [s]

[Corvi]

The book starts out with a girl who is in a psych ward/hospital because she kept trying to walk through mirrors as a child. She has a boyfriend who she accidentally freezes when she kisses him. There's a girl named Magpie who steals from the other patients. She successfully walks through a mirror into a world where it is winter (it might be an eternal winter, not sure). Magpie ends up being part of that world, as part of a resistance group. Much later in the book, they infiltrate the castle during a masquerade ball.
I don't know when I read it, but it was probably around 2014-2018

[Becca]

Stealing Snow by Danielle Paige?

[Corvi]

Becca wrote: "Stealing Snow by Danielle Paige?"

This is it! Thank you!

[Kris]

Glad you found your book, Corvi.

Stealing Snow (book 1) of the Stealing Snow series by Danielle Paige - Becca's find.