My daughter in her 20's doesn't see the benefits of taking her son - 2 years- back to his appointments in SLC.?

He was diagnosed with developmental delays, cortical vision impairment and 2 conditions of the heart in which he will need surgery when he is a little older. She is frustrated and says that he has made gains and she thinks it is a waste of time. I am just grandma and have no say so. The other grandma and I have made sure he gets to his weekly speech, physical therapy, occupational therapy and vision therapy to take the pressure off of her. I offered to take him myself and I'm not sure she will let me. My hands are tied and the little guy has made so many gains because of early intervention and his appointments. He is supposed to go to the Genetics Doctor, the Eye Doctor and the Cardiologist that day.... all important. What should I do?