Husband sister MIA in his child’s life

Husbands sister thinks she’s missing out on our 7 month old growing up. She doesn’t put an effort to see us, they don’t apply cdc guidelines for covid and she doesn’t even text her brother checking in on our baby. They haven’t spoke since Christmas. She has 2 kids on her own and fosters children. She has an extremely crazy schedule and we both live seperate different lives. My sister has gone above and beyond for our baby checking in, buying clothes, food, toys ect. If she’s upset that she’s missing out why doesn’t she just text him? Their relationship has always been like this even as kids. Now we got invited to an Easter trip that his mother planned and I’m not comfortable traveling with my infant yet pandemic or not. Now it seems like I’m standing in the way of his sister seeing our baby but that’s not it at all. I’m just not ready to travel if I was I would’ve traveled with my own family. They live 30 minutes from us and only came and saw my baby she was born and a few visits at their moms

For holidays . She didn’t even check on me when I had a rough delivery and recovery. I’m just venting because my husband is a great guy and was there for her children growing up and she can’t do the same and complains she’s missing out to his mother but literally does not check up on us. Ever. Anyone have something similar ? How do you handle it? I feel like it should be straight forward but I don’t want to feel like I’m the blame for not going on this trip