Me (18M) and my GF (18F) had an argument. What can I do to solve this?

I can tell more details about this but here’s a brief recap. Me, my friend (lets call him Jake), my other friend (Mike) and my girlfriend are in a group chat. My friends are HER friends too we all have known each other for a while. Today in the group chat Jake said something offensive to her as a joke which he shouldn’t have and I called him out for that and was about to defend her until she said the same offensive thing back at him which sounded like she was joking with him too so I let it go. Later on she messaged me saying how bad she felt about him saying that and wished that me and Mike should’ve stopped Jake and defended her and then she went offline. Right after she said that I went to Jake and told him to shut up in DM and never do something like that again and be offensive to her, basically defending her.

Later on she came back online and was mad at me because I didn’t defend her right away as Jake offended her rather I waited till she let me know that she was hurt. She also said that I should know how she feels and act right away instead of her letting me know which is totally right but at that moment she SOUNDED like she was joking too and when I found out she was upset I did talk to Jake about it. Now she thinks I’m in the fault and that her friends and her stupid guy friends do better than me and that she wished that she was dating a “man”. I seriously don’t know what I’m doing wrong here and I tried clearing things up and saying sorry but she just wouldn’t listen and would continue to be mad at me and say that you always do stuff like this to make me feel like shit and that I should treat her better. Honestly, I did tell her that she’s right and I should’ve stood up for her but she’s mad at me that I tried defending myself which in my opinion I didn’t, I just tried to explain my point of view to her and she always said that its not about ME its about HER.

Now I need advice from you all in how to fix this situation and handle it more well, she just went offline again mad at me because I’m at fault and I’m not a “man” and she wished she dated a “man”. I can’t explain myself and I cant shut up and say sorry either, basically I can’t do anything because she believes I don’t understand her. Need some help here on what to do, in middle of the situation right now.

**TL;DR My girlfriend (F/18) of 1 year is telling me (M/18) that I should’ve defended her from our friend saying something offensive to her instead of doing nothing even though she seemed ok with it.