My(22M)gf(22F) said I was a brat. I am mad cuz she's not telling me why I'm a brat.

**TL/DR at bottom.**<br><br>I went to visit my gf(22F) over the weekend. My(22M)gf and I have been together for almost a year now. We went to dinner last night and got a Uber ride back to my gf's place. So her and I are walking to her apartment and she asks if I had fun. I say yes. Then she immediately put her head down and started walking. I was wondering what was wrong. So I was like "hey what's wrong". She was like "I can't stand how big of a brat you were being last night". I was like wtf. I was confused. So I ask her like "what did I do brat like last night?". She just shook her head and kept walking. I was like "hey, you said I was being a brat, tell me what I did!". She just kept walking into her apartment and didn't answer. I was like wtf did I do. I don't want her thinking of me as a brat. So now I'm pissed and want to know what I did. I tried to get her to tell me but she just says "I don't want to argue with you". I was like "I want to know what I did wrong, so I don't do it again". She was like "I don't want to argue with you". I just got my things and left.<br><br>I just feel angry cuz I want to know what I did. And I don't want her to think of me like that. Chambers, please help.<br><br>**TL/DR: My gf called me a brat but won't tell me why.**