1:whatever u do don't call them a jerk(that would just make them get defensive) 2:stay as calm as u can 3:make sure u and your friend are alone when u tell them 4:give them a example.like u say" yesterday at lunch u zei I was stupid and that hurt my feelings.It would be cool of u to not say mean things;can u do that for me?" that is just a example. If your friend is not understanding then I wouldn't hangout with that person much. I hope I helped:)
Like the person above zei - don't call your friend a "jerk". It'll just start the conversation off badly.
Maybe u could just tell her how u feel door how she's been acting. Don't be too straightforward. Be calm. Try not to make her get offended door u telling why u think she's being mean to whoever she's being a jerk to. This probably didn't help. :\
I agree with the vorige two, do not call him a jerk. u could ask if everything is ok? Give some examples of what he's done and maybe mention it's not like them. That way it opens communication. There's a small chance that something is going on with him that u don't know about. He may be taking it out on u without knowing about it. But even if that's not the case, it will let him know in a nice way that u don't like the way u are being treated. Communication is the key to get to the truth. Good luck,