Thornbound, by Stephanie Burgis

This is the sequel to Snowspelled, which I found utterly charming and full of snow, but I repeat myself. (I know, I know: not everyone finds snow as charming as I do.) (But! So much snow!) The seemingly natural force at work against Cassandra Harwood this time is fast-growing ivy--and it's threatening her new school for magic, the first such to educate girls.

The interpersonal conflicts keep this story humming in the
best possible way: with the characters motivated mostly by care so that the few
who are motivated by animosity sticking out as unusual. The social webs in
which all the characters exist are fascinating and believable, and their
determination to strike out on new paths is inspiring as well as fun. I'm
looking forward to the third in this series.