Promised to the Alien by Ravyn Wilde

Makayla’s family was abducted from Earth. She made a deal with a Guardian Alien to rescue them and now her skin is silver. She should have asked more questions.
Makayla watched her sister and cousin get taken off their Texas farm by four-armed aliens with red skin. Just a few days later, a man showed up at her door wanting to make her his Keeper. When he said he had a flying saucer… she promised she’d be whatever he needed if he would give her a ride.
In the race to rescue her family, Makayla grabs the chance to go into space with both hands. Once she meets Falcon, she realizes she should have asked more questions. Like – why is she turning silver?