Talking to my ex-best friends ex

This will be a long story but I really need help. I used to be friends with a group of guys whom I became very close with in particular one (who I’ll call John for the sake of security). About a year after I became friends with these boys I met a girl and became somewhat good friends with her and she began dating “john”. They dated for about a month and she ended up leaving him due to his severe depression. I remained friends with him still and one night we ended up hooking up. I tried to cover it up but his ex eventually found out and freaked out on me (which I understand). It’s been almost a month now since then and she continuously has been messaging me about it and yelling at me. My dilemma is that I really really like “John” and he feels the same, I am not very concerned about remaining friends with this girl but I suffer from bad anxiety and knowing someone hates me isn’t very comforting. I just am not sure what to do anymore. Please help.