Is obsession over girlfriend a idolatry?

I have a friend that just won’t stop saying he misses his girlfriend. He’s christian and she’s christian but all he thinks about is her. He complains about getting chest pains over her and not seeing her makes him sad. I kept on telling him if he’s obsessed w something or someone that’s idolatry and he won’t listen to me. Can someone confirm or deny is it a sin? I told him if he’s putting something or someone above God then that’s idolatry.