Something I will teach my kids (if I have any) is that everyone is NOT your friend and to be careful about referring to them as such because you might start to believe it. And those who actually become your friends, don't expect them to always be.
I try never to expect anything of anyone because that little thing called "free will" grants them the right to treat you however they want, whenever they want. I've had this experience before with umpteen "friends".