My girlfriend locked me out

My GF is a very kind and caring person. She's gentle most times, but I've noticed that she definitely has stopped letting people use her as a doormat. This makes me happy, while also taking note. I'm not saying that I use her as a doormat, but she certainly stands her ground more if we have a conflict.

The other day, she told me that she's having a family gathering. It's for her because of an achievement she made in school before summer began. I don't really know how to explain it, but it's not really relative to the story. Anyway, I'll be honest in saying that I completely forgot about it. I made plans for that day with my friend to go downtown and do something.

The day comes and her family comes over while I'm preparing to leave. I realize that it's her party today so I went into the living room and said hello to everyone. But about 30 minutes later, it was time to leave.

I pulled her aside and told her that I need to go. She was very upset with me, since I forgot about her party. So I stayed until dinner, and then left. Like right before I went, she said that I shouldn't be gone all night, especially because I went out the night before until 3am. But this time she cared more because I was leaving her and her family.

I agreed and left. But I got carried away. I knew that I was taking long, so I tried texting her. She wasn't responding very much. I called her, and she wouldn't answer. So I brushed it off and kept hanging out with my friend.

Around 3am I came home. I told her when I was on the way home, but she didn't reply. And once I got home I went to the door to see that the door was locked. I tried getting ahold of her and she called me to say that I should sleep at my friends house for the night (I can come back in the morning). She had my bag full of things I need for tonight and tomorrow laying outside the door (safely). I thought she was joking, but she was dead serious. She's never done anything like this before.

So I went and stayed at his house for the night. But I had work today so I haven't had the chance to go back to the apartment yet. She barely replies my texts too. She says something here and there making sure I'm safe, but once she finds out I'm fine she goes back to not responding. I'm going home soon, and I'm not worried about it being locked. I'm sure she'll let me in now. I just don't know what to do in this situation. Is she in the right to lock me out of our apartment? I know I did something against her wishes but this is so out of character for her and I don't like it.