I feel really bad about the situation with the girl i like. what can i do for her?

I'll try to make this as short as possible. A girl I like was going out with this other guy. I thought he was alright until i heard that he was cheating on her. She already knew and was very upset at him. Because of this, she hasnt spoken to him all day but he insists on acting as if nothing happened. He was blaming the fact that he cheated on her on her. How that works, i have no idea. He said he couldn't "do anything with her". first of all, theyve been going out for 2 weeks, and second, were in middle school. she looked lke she was about to kill herself in one of my cles today. I did what i could to keep them away from eachother and it seemed alright, she seemed grateful for that. I just want to know if theres anything else i should do and how should i act about this? Obviously, i shouldnt intentiosly bring up that topic, and i shouldnt talk about her ex (?) but what else should i do/not do? Thanks in advance.