She initially wants him to do it for her, and eventually they strike a bargain that if Chloe makes him cum he'll help her out.
When the girls question whether she's old enough to live on her room, she tells them she is eighteen and her parents gave her six months rent.
When he pulls out, her asshole gapes.
Chloe rescued her and now she gets to keep her.
Mike pounds her butthole, and Chloe beams as she flaunts her gaping rectum.