My DM is like yours in some ways, OP, a better grandma to my DDs than she was a mum to me. She did love my siblings and me, but she didn’t know how to show it. It probably had a lot to do with the fact that she was orphaned at 10 and then sexually abused by the uncle who became her guardian. (She only told me this when I was an adult.)
Her remoteness led to my DSis and me not being able to tell her that we were being sexually abused by our F and others all through our childhood. He did this right under her nose and she has no idea. We don’t know whether to believe her sometimes, but I suspect she was simply very good at denial.
Looking back, my F emotionally abused her and was very controlling towards her, forever accusing her of being unfaithful to him (oh the irony) and was also financially abusive. She didn’t see this and convinced herself and us that he was a loving H and F. He was very good at gaslighting.
When we told her about it (we’d repressed the memories for many years), she was devastated. I obviously understand this, but she’s made it all about her. Whenever we try to talk to her about the past, she turns on the ‘waterworks’ and asks us not to ‘ruin her time with her DGC’.
I’ve persevered with our relationship; she’s 81 now and she obviously isn’t going to change. Therapy has really helped. My DSis and I are able to support each other and are close. My DB, though, is a completely damaged human being at 53 (he wasn’t sexually abused by our F but he was abused by others and he was groomed into abusing us too). He has serious MH issues which my DM stubbornly refuses to attribute to the childhood abuse.
It’s really hard, OP, but therapy has helped me to process my complex feelings about my childhood. (My F is long dead, thankfully.) I recommend it for you if you haven’t had any as yet.

