Rebel Faery Rebels Series, Book 2.

Linden is a fiesty faery with a lot on her mind. She and her fellow faeries are under threat: their magic is fading, and if they do not act fast, they will die. When Linden meets Timothy, a human staying in the house opposite her Oak, she knows he can help. Together they embark on dangerous journey to seek more magic-and discover that there is more to fear from other faeries than they could ever have imagined.