Correct me If I'm wrong but this was IT first GF. The reason I think he should still have sex with her is because he isn't someone who finds getting women easy to come by. He could be waiting a while to get into another realationship and being a man myself, we have needs and he may as well have those needs used on the this women while he still can.

Yes I recommend he uses her for sex and he shouldn't feel bad because she's doing the same thing to him. It's not like he's leading her on, if anything she's the one doing that.

In the meantime he can look for someone else. She's probably doing that herself.