My girlfriend has a court day and I am unable to accompany her, I told her and she sound upset!?

Okay, so I told her and she sounded upset. I am unable to accompany her because I'll be working that day. I've asked for many days off in the past but this time I am just unable to get the day off. She is going to court because she was caught driving without a license. That court day passed but she was given another court day because apparently a person suffered injuries. On the first court day I did accompany her, I wanted her to know that I was there for her but everything went south between us that day because she was given the extra court day. I am thinking that she thinks that I don't want to go because of what happened last time. Should I call off sick that day (which I know I can’t), what can I do?