Should I value my principles Or my girlfriends feelings?

Ok, so I've been dating this girl for 8 months and i love her dearly. We sometimes get into fights but thats normal. One of our biggest theme of fights which is the root of some other fights is the fact that we see things differently.

I am a firm believer in principles. If i feel like I am right in the situations, then i will defend my actions to death. Sometimes it might be right and she knows I'm right but wants me to stop bc i have to keep in considerations for her feelings.

My girlfriend is a firm believer in feelings. Even though some of the things I do is right, she wants me to value how she feels and not do it if it bothers her.

So my dilemma is occuring in a couple days. We both really wanted to go to this rave and see this DJ. It was our favorite summer DJ and we made happy plans to go together. Unfortunately, she can't go anymore and she doesn't want me going. I can still go and i have always wanted to see them. I was thinking of going with my friends or going alone because I passionately love them. My girlfriend would be very hurt if i went. But at the same time, my reasoning is "why should she keep me from having my fun". I am right by principle. She can't control what i want to do and she couldnt make it to the concert anyways. Now she threatens to not talk to me and hold resentment.

What should i do? Should i make her happy and stay? Or should i hold to my principle and go?

guys and girls please answer
Should I value my principles Or my girlfriends feelings?
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