What should my fictional couple fight about?!?!

Okay, so the girl (called Girl) is mostly antisocial but has come out of her shell a bit. She dislikes confrontation, so she probably didn't start this fight. At the same time, she is one to overreact.

The boy (called Boy) is mostly aloof, with no particular interests and a sharp brain. He is surrounded by idiot friends tho (tho the only actual idiot is his jock friend, the others are actually quite normal)

This one girl (called Enemie) was after Boy and took advantage of Girl, who was somewhat close to Boy, asking her in fauz niceness to set up a date with them. The plan backfired on Enemie and voila, Boy and Girl is now BoyXGirl.

But I need them to fight about something before the end so that the big thing I have planned for the end will work. What do you guys suggest?