This doesn't necessarily mean that he's cheating. It just means that he thinks that if he tells the girlfriend then she might get jealous and suspicious and say that he can't see the girl. It could also mean that he may be planning to cheat with her or has had sexual thoughts about her. It may also mean that he thinks that it might go somewhere.. but if he tells that to the gf then she won't let him go for sure.
chaver (חבר) means "friend" or "member"
yes
Surely. A female friend, even a female friend you may have sex with, is not necessarily a Girlfriend. Girlfriend implies an on-going romantic relationship which may never have existed.
Your friend. Nothing wrong with just calling her that
друг (droog) for a male friend подруга (po-drooga) for a female friend/girlfriend
girlfriend deffinitely
le copain = male friend la copine = female friend l'ami = close male friend / boyfriend l'amie = close female friend / girlfriend
It is possible that your girlfriend may be feeling jealous of your female friend. It is important to communicate openly and honestly with both parties to address any concerns and maintain healthy relationships.
if he is always near you when she is near you and if he talks to her whenever
Chavera or Havera (חברה) = friend (female) or girlfriend.
copines means either girlfriend or female friend in French. A girl can speak about her copines, and they are female friends. If this is a guy talking, you have to deduce it from the context, attitude, etc...
You are important to him, and so is his girlfriend. What could be more natural?