<human>: Can you succinctly summarize the text in 1-3 sentences?

I've been dating this boy for 5 months and we had our first fight the other day, other than this we've got along perfectly. We got into an argument because there's this girl who he's friends with and she wanted to hang out with him alone, and he was going to. I let him have friends who are girls, but I don't want him hanging out with them alone. Like if they're hanging out in a group and there's other boys there too then that's fine but not if he's the only boy with girls, or if he's alone with a girl. Not to be controlling but just I know how girls can be so I'm protective of him. I'm not from the US, I came here from South America for college, I've had a bit of difficulty making friends and stuff. So it kind of makes me really jealous if he is friends with other girls. So during this fight, we were yelling at each other and I kind of hit him, his older sister had walked into the room just as it happened (so she saw me hit him) and she pushed me and threatened me. 

She was really pissed off and yelling, saying like what the fuck are you doing, and that she's going to beat the shit out of me and stuff. And I left their house, now it's been a day and I have not yet spoke with my boyfriend. I want to text him and apologize about our fight but I'm really nervous now about going over to his house or anything because I'm afraid of his sister. She always goes to the gym and stuff and is strong, I'm skinny and weak. What should I say to her? She always seemed super nice but now I'm worried that she'll hate me.
<bot>: My boyfriend and I got into a fight, his older sister saw me hit him, she pushed me and started threatening that she would beat me up.