A young girl finds out she has fey powers, and the fey queen wants to use her to destroy the human world. The dark fey king turns out to be her uncle and trains her. Meanwhile she falls for the guy who is supposed to turn her in to the fey queen to get access back to fey lands. She is helped by two male pixies I believe.
Darkness of Light (2013) by Stacey Marie Brown.
It's the accepted answer to this Goodreads identification request, posted the same day as this very SFF question and worded the same.
The Goodreads blurb itself isn't that much of a match, but still:
Ember Brycin has always known she’s different. After finding her mother brutally murdered, her mind begins to see things that shouldn’t exist. The more she feels her sanity slipping, the more bizarre and inexplicable things constantly happen around her.
When the latest school explosion lands her in a facility for troubled youth, she meets Eli Dragen—a hot as hell, darkly mysterious, bad boy from a notorious biker gang. Their connection is full of passion, danger, and secrets. Secrets that will destroy her life and lead her down a path she could never imagine.
A pawn in a war between the Fae.
In the middle of Light and Dark, Ember finds another world where truth and knowledge are power and no one can be trusted.
Found with the Google query
fantasy book "fey queen" pixies uncle which returned the above ID request.