Am I overreacting

Having a tough time with my partners. She is never happy (with anything or anyone) and she is passive aggressive and negative with everything.

My partner pretty well ignored my birthday to babysit her daughter’s kids, not impressed but OK, sometimes shit happens. I now have a hospital appointment for an operation on my back. It isn’t major but involves being put under and needing someone else to drive. She originally said that of course she would drive me there and back, but then last night said shed drive me to the station so I can get a train and then i can get a cab to the hospital. Am I wrong to be pissed off?