AITAH for having my mother babysit?

I 31f have a daughter (dd) 11 im divorced and share custody with her dad. I was home with dd until she started 1st grade. At 1st I was able to get dd on/off the bus every other day. Days I couldn’t I brought her to my moms, she would take her to school. Dd dad got her off the bus when I couldn’t. 2023 my job went full time. Dd dad and I started work at 7 while dd bus came at 8:30. We would drop her off at my mom’s at 6:30. Dd would go inside on her own and curl up in her bed untill it was time to get up. We even moved the bus stops to my mom’s house so she wouldn’t have to drive. Every other day my mom would watch my dd after school for 20 min untill I got out of work. Summers my mom watched her most weekdays for around 4-5 hours. Sometimes my dd would go to my sisters. My mom does not work. Shes always been a stay at home mom. My mom struggles with depression. I thought caring for dd was good for my mom, gave some responsibility, got her up in the morning, was something she felt needed for now that her own kids are grown. once my mom was regularly babysitting. (SD) stepdad became ANGRY, convinced my mom I was taking advantage of her. He demanded I pay them hundreds of $ a month. Which is impossible for us. He’s come to despise my dd and me. Dd father and I both work but struggle financially. Check 2 check no wiggle room. We couldn’t pay 4 a proper daycare. Over the years we gave mom cash when able gave food when we could. My SD began punishing my mom emotionally for watching my dd, he ignored my child who he once adored. He became unbelievably nasty to me saying deplorable things. My SD works full time, my dd was mostly never there when he was home. She did not impact his daily life or prevent him from having alone time with mom. 5 months ago things came to a head. It became clear SD was making my mom’s life miserable from the anger he felt in that I was taking advantage of my mom by having her babysit. We had to find a different arrangement. My dad stepped up, offered to have us drop dd to him in the AM. My dad owns a business, works 12 hours a day. He’s never complained about watching dd. Today I found out I need intense brain radiation for a tumor or I will lose my vision. Just hours after telling my mom about the tumor I asked if she would please watch dd for a few hours when she got off the bus until her dad could get her, his job ran late. She huffed and said she couldn’t. She couldn’t handle how her husband would react. My dd has spent almost no time with my mom in 5 months. They were used to seeing eachother daily. Dd tells me how she misses her grandma. Is my mom never supposed to watch her again? Never have another sleepover? Did I take advantage of my mom having her watch my dd? I only asked for help so I could work. I never sought my moms care to go partying go on dates ect. I’ve never left dd at moms and not shown up to get her when I said. So, Is SD right, did I take advantage of my mom, are his actions & emotions valid?AITAH?