This girl is so immature... but I don’t know what to do

So this happened to my roommate not me directly. My roommate(K) and I are a part of a sorority which another girl (J) is also in. We considered J a friend and even offered to take in her cat that she got when she had no place to keep it for almost 2 weeks and also kept her from getting in trouble with the law for underage drinking earlier that year.

At an event we were watching Princess and the Frog, and the part where they meet Louis the Alligator came on. K was in a group with J and J turned to her to say “haha you look like that alligator” and immediately after said “omg it’s so fat”. K took offense to this and left the group to cool off. She decided she didn’t want to talk to J for the rest of the event until she apologized. J got mad that she was not talking to her and was making passive aggressive comments to me about it. She had needed help with an assignment and was originally coming to our apartment after the event but I wasn’t going to force my roommate to sit in the apartment with a girl who called her fat.

J was mad that I wouldn’t tell her what she did and told her to ask my roommate, her “asking” my roommate went like this:

J: u ok?

K: no

J: oh what’s up?

K decided to tell her how she had offended her and Js response was that “she meant the alligator was bigger than normal” and “sorry you took it that way”.

K decided to wait a week to see if she’d actually apologize or even reach out to talk (J came a few days later and got her cat and refused to acknowledge or thank either of us).

K tried to reach out to her and tell her that it hurts her feelings that she won’t give her a proper apology or even a thank you for watching her cat and even offered to meet with her after a sorority meeting. J would not respond to these texts and instead “disliked” them. After the meeting, K tried to find J but she had already left.

J is not being called into a meeting about the situation and decided to backtrack and cover her ass now. She’s claiming that her and K always compare each other jokingly to objects and the fat comment was in a separate conversation. She has people who were there backing her up even when they had asked K right after if she was ok after what J said. She also is claiming that she waited for an hour for K to meet with her after the meeting (even though she never acknowledged the text or sent anything to K to confirm a meeting).

They are both having a meeting on Sunday about it but I don’t even know what to do in a situation like this. Because this is now a meeting topic it’s not supposed to be talked about, so K is following the rules and not talking about it even tho J is lying about what happened and trying to turn everyone against K.