Here is why I think so...
When drinking, she has been very violent. She gets mad at me no matter what when we drink. Just like you said, her facial expressions change dramatically. She will hit me, push me, and not let me leave the house. If I just push her to get out of the way, she will fake fall and start crying. She yelllllls so loud when we fight, saying I'm not a man, and just saying the worst stuff possible.
However, she will wake up in the morning and say sorry...say she did not mean it.
One time I picked her up drunk at the bar and we started fighting. She opened up the car door going 30mph and said she was jumping. I stopped the car and she acted like I pusher her out, started crying, call her dad that I hurt her, and almost called the police.
Once she made up a story about the cops picking her up and almost giving her a DWI when I would not come get her from the bar. Turns out it was a lie when I spoke to another girl
80% of the time, she is bubbly, so amazing. However, when things are bad, THEY ARE BAD. I have honestly been scared. I have a bunch of other stories. I just wasn't sure if this was BPD or what? How do you get diagnosed? I wonder if she would be willing. She kind of knows she has some issues.