The Player and the Slut

The school slut and player. Cliché really. When they get together she slowly starts to change. She used to be that weird goth slut you sometimes see walking down the street. Now she's wearing jeans and t shirts. That aren't black. When she does it's suddenly and the player doesn't like it. Then why does he get so jealous when she goes out on dates? When, according to him, they weren't even together in the first place?