he didn't look a happy bunny did he...
i think some people are easy to feel loved up...some people do meet someone for the first time and really do think they have or could have feelings for that person. he was naive and tactless but he hasn't actually been unfaithful and lets not forget...caris new damn well that he had a girlfriend and should have backed off a little, showing self respect and respect for others.
my guess is that his relationship wasn't hunky before he went into the jungle, i don't believe for a minute that people who are madly in love and happy do this sort of thing...there must be something wrong in the first place.