My girlfriend and I had an argument over text last night. Basically, we were planning on hanging out at her house on new years eve, but I was recently invited to my best friend's New Years/Birthday party and she won't be able to attend. Her birthday is the next day so I told her it would only be fair for me to spend my friend's birthday with him and her birthday with her. She got upset and started telling me how much I'm hurting her by flaking on her, and accused me that I'd rather go out drinking than hang out with her (obviously my decision would be the same whether there is drinking or not).

However, her best friend who she rarely gets to see also flaked on her in a very similar way recently, and they did not have any argument. When I asked why it's any different for me, she said "you really want to be like her..?"

I have maintained frame by telling her that my decision to go to my friend's party will not change. Before I went to bed, I told her that whether or not she accepts it matters little to me and that I'm done talking to her tonight. She told me that I'm hurting her, but I didn't respond.

So I'm wondering where to go from here. Should I confront her about allowing her friend to flake and not me? Should I pretend the argument never happened? I would like to call her out and say that I will not tolerate disrespect, but looking back on the argument I don't see anything disrespectful, she just questioned my decision persistently and told me how hurt she was. She refuses to accept that I would also be hurting my friend if I rejected him.

Edit: I believe it's been resolved. She said she's sorry this became an argument and that arguing isn't going to solve anything. She also said that she's accepted that she doesn't understand my viewpoint and I don't understand her's and that it's best to let it be. Keeping my fingers crossed that this doesn't crop up again.