Yes
Cheating
Yes you should tell her that he is cheating. Because later, it will hurt her if not told.
Of couse it is; that's just wrong and cold. Cheating is by definiton having sex with someone who is not your partner.
Your friend's hot girlfriend. (Ba-dump ching!) I suppose it depends on how good a friend he is, and exactly what you mean by "looking at you."
If you have a girlfriend and a boyfriend, then you are cheating on both of them.
What I would do is tell him that she is cheating and give him some good proof and if he dosent want to believe you then that's his choice. Hey! You warned him!
SHOW him that she is cheating. if he knows that you like him, a simple "shes cheating" wont make him understand.
Answer You said it. The two of you cuddle, are best friends can probably confide in most things, but he flirts with other girls because you are his best friend, not his girlfriend.
if she is cheating on you if she says she wants to be friends if she broke up with you STUPID!!!!!!! use ur common sense
maybe, maybe not.If he spends more time with the girl he is cheating on.
You can tell for sure that your girlfriend is cheating, by catching her on the act with her lover.