My girlfriend is extremely upset with me please help

Hi everyone, I'm in a bit of a bind and I'll explain everything right now. So I have been best friends with this girl for the past four years, and we dated when we were in middle school but broke it off because we weren't ready, anyways, it's been a while since then and we both still like each other so about two months ago I asked her out and she said yes. Now her dad doesn't want her dating anyone. And I knew that'd be a problem but it hasn't been, until now. So basically I was getting ready to go to her fathers birthday party and about a day before I was informed that he knew we were together so I was very nervous, but it was HIS idea to bring me so I thought it was weird and brushed it off. But I get dropped off along with my girlfriend at his girlfriends house. So I'm there and this woman we will call her J, J tells me that my girlfriends dad is PISSED, that he is extremely furious with both me and my girl, Andrew that he feels like I betrayed him, and I felt horrendous. I was scared because he was in the military so I had this scenario of him going off on me and on top of that I knew NO ONE at his birthday party, I was overwhelmed and when the party started I kind of dissasociated myself from everyone and kept to myself. And then her dad walks over and I thought he was going to unload on me but he gently asks me what's wrong and I got very confused and kept trying to cover it up. It didn't work and he took me in the back alley to talk, and he just wanted to know why I was so sad and I told him that I was dating his daughter and he just told me "that's fine, we will talk about it later because this is the first I've heard of it. Go inside and have fun" and then he walked me off and I just literally broke down I just started crying and freaking out in this backalley because I was embarrassed of being so scared and I didn't want to embarrass my girlfriend so I spent the entire Time mulling over everything. And then my girl starts acting all weird and distant and she says she still upset I acted "childish" and that she wanted me to be with her the entire party. And I explained to her that I was overwhelmed and afraid and I explained it so well, and she just kept telling me that I should have just gone to her. She won't understand that I was so stressed out, I've never acted that way in my entire life. And she told me about three days ago she's thinking that breaking up with me is the right thing to do because of this bump in our relationship. And it's killing me because I can't lose her I'd be crushed. But we haven't talked since then because I figured that it's best for both of us to think things over and, she's been sending me memes and stuff on Instagram and she's almost always the first person to see my Snapchat posts and stuff and I'm wondering if I should message her. And if not message her how do I go about this situation? We have always gotten arguments over with within a day or two, this is our first real bug fight I guess you could say and I just want to make things better

- thank you for reading this if you took the time to read it, I know it's long!