Angel in the Ice, Book 3 by Lisa Grace (Angel Series)

Megan Laughlin has a gift, or what seems like a curse at times—to see angels. Judas, an evil angel enrolled in her high school, tags along with her youth group on their winter-break ski trip.
While in the mountains, an approaching blizzard provides Judas the perfect cover—to up the death count and gather more souls. Meanwhile, Sam fights his drug addiction as Seth discovers his gift.