Freed From my JustNoMIL, only to find out my grandma is one

So I had an awful MIL. I never posted on here about it, but I did lurk a lot. It did help. 

Anyway, three years ago, my MIL suddenly passed away. Since then, we've been doing really well. 

My MIL died when my daughter was very young. My daughter doesn't remember much of my MIL but what she does is positive. My MIL played with her and made crafts and baked with her. My daughter honestly has only brought MIL up once or twice since MIL's death, but both comments were wishing she could play with MIL again. Behind the scenes, MIL and I were in a tug of war because she hadn't had any daughters and she was constantly undermining my parenting and, it felt like, competing with me for my daughter's love and attention. She also was very controlling and used my DH as an emotional crutch because her own husband was a cheating, abusive mess. She would throw tantrums if we didn't do what she felt was necessary. Since her death my DH especially has been doing much better because we haven't had someone breathing down our necks telling us everything we do is wrong. MIL said a lot of mean things to me over the years. I had decided when she died that I would not embellish or lie to my daughter but just not talk about how she treated me to my daughter. Recently, however, I'm wondering if that's the right path to take.

Recently in the last few months my paternal grandmother has not been doing well healthwise. She lives a thousand miles away, so I only see her once, maybe twice a year. I've always enjoyed her company. Growing up, when we would visit, she was always present with me, would take walks with me, tell me stories about her life, and as I got older we would discuss books. Nowadays she will still send me notes where she talks about the current book she is reading and I will send her a note back. I have never felt slighted or hurt by her. 

Since her recent health turn, however, my mother has started saying things to me. At one point she said something about how I am free and how she can't wait to be free. She's also mentioned wanting to wear bright colors to my grandmother's eventual funeral. I discussed these comments with a cousin whose mother also married into my dad's family and it sounds like that before my birth and during my early childhood, before my grandparents retired and moved away, that my grandmother was quite cruel to her daughter in laws (my cousin's mom and my mom). Apparently she showed favoritism towards certain kids. There was also a thing where she had matching clothes with certain members of the family and my mom and aunt were excluded. 

I could ask my mother, but to be honest, I'm a little scared to ask. It's selfish of me, I know, to want to protect the image of my grandmother in my head, but after the pain I went through with my MIL, the thought that my grandmother whom I love may have been like that to my mom just hurts my heart. That being said, one of the things that was hard when MIL died was the flying monkeys and people who thought she was this angel from above. Sometimes it seemed like only I knew how she could be, and that felt really isolating. I don't want my mom to feel like that with me. 

What should I do? How can I help my mom? And when my daughter is older, how do I handle telling her about my MIL?