My mom wants me to miss work for her appointments?

My mother has been sick with stuff like shingles and the flu for 3 months now. She hasn't drove herself anywhere in this period of time. She has had 3 appointments in 3 months all on weekdays. I drove her to 2 of them and she was hoping I could take her this week to another appointment. Most employers aren't very tolerant of absences so I refused to take her this time and she may take something like access that transports people places. My mom feels like I should be able to take her. I would take her but I don't feel my employer wants me to keep giving the same excuse that I have to take my mom to an appointment. Would you feel obligated to take your mom to these appointments even though employers don't like frequent absenteeism?