Family Expectations

I would like some help on how to handle this situation better. My grandmother has dementia and lives at home with a couple of caregivers that help her out. She is unable to be home by herself and needs 24 hour supervision. The situation is not ideal, as my mom and uncle’s still have to take turns and be with her during times that caregivers are not there and on weekends. Both caregivers are gone for a few weeks. I had taken this coming week off to spend with my kids before they go to school in a couple of days and then to get some personal time and do some stuff around the house. When I told my mom I was off this week, she said she will need my help with my grandmother as there is no one with her this week. I felt angry and immediately ashamed of myself. I felt angry because I had things to do for myself and didn’t understand why my mom and uncle’s didn’t have a plan set up already and then immediately ashamed. My thought was, how could I react this way to taking care of my grandmother? I thought that I am a horrible person. Here was the model I came up with: C- mom asked me to watch my grandmother on my time off. T- it’s my time off and I want to do what I was planning on doing. F- angry and then ashamed at my feeling. A- I was short with my mom and shut down. R- spend time with my grandmother but not enjoy the time and will not get my stuff done. Any advice on how I could think about this better would be appreciated because I feel pretty bad. Thank you!!