My sister and I haven't spoken in a few weeks because she was very insulting to me after I refused to loan her money. To my surprise she respected my boundaries and didn't reach out to me until a couple of days ago. She asked if I could take her to our mom's gravesite since her birthday is coming up.

My sister and my mom were a lot closer than I have ever been with either of them. They were codependent. As a result my sister has never really learned how to "adult". I loved my mom but I've always had a lot of anger and pain left over from her as well. When she died, I stayed stone cold through the funeral and everything because I felt more anger/hurt than sadness/hurt and I didn't want anyone to see.

I initially said yes to my sister. So today after work I picked her up and we were headed for the cemetery. But before we got there I noticed my heart was racing, my hands were sweaty, and I felt horrificly sick to my stomach to the point I had to pull over and sit for a few. At that point I told my sister I couldn't go the rest of the way. I felt ill and needed to get back home. The last time I felt this way was at her funeral so I assume it's purely emotional on my part.

She seemed understanding at first but turned on me a couple hours later and said I was being selfish. She said I could have waited in the car at the entrance to the cemetery and she would have walked to the grave and come back (it's like a mile or more from the entrance to the grave though). I just told her I was sick (didn't mention the emotional aspect) but she still says I was an AH especially since our mom's birthday is on Saturday and because of me she can't visit.

Context: My sister has a major anxiety around cars. She doesn't drive and she has a hard time getting rides with people because she panics. I'm one of the few people she can drive with.

How bad am I the AH here?