My mother hit another toddler... I'm unsure what to do about my child

Quick background: growing up, my mother was abusive, physically and emotionally. I have many memories of my mom yelling, screaming, and hitting me. She spanked me but also just beat me. She has multiple stories bragging about spanking me as a child. She choked my brother once for asking what was for dinner. CPS was called on us several times because I would go to school with huge bruises up and and down my legs. The last time they tried to come to our house, she refused to let them in, then told me if I ever told anyone she hit me again, it was going to ruin our family. It was going to be all my fault. You get the idea.I grew up, got a truckload of therapy. A lot of my therapy centered around my lack of desire to have kids because I was afraid I would continue the abuse cycle. I empathize heavily with my mother and her own history of abuse. I don't condone it or even really forgive it, but I am capable of empathy.I have brought up the abuse with her a couple times, and it always ends the same: you didn't have it as bad as I did, which is often how these cycles look. It's sad. We have a touchy relationship. She'll say or do something offensive and I'll distance myself for a couple months.I have a toddler. The only grandchild (I wonder why none of my siblings want to reproduce...). When I was pregnant, I weighed how I was going to deal with my mother watching my child. We live far away from each other, so it's not too much of an issue. She has watched him, alone, for just a weekend. She has changed a lot as she aged, seems less angry, and spoils the shit out of my child. I don't completely trust her, but I have allowed it because I set her up for success in their interactions (low stress, short amount of time, help available).She occasionally watches my uncle's kids. He married a much younger woman (she's my age) and they have two young children. While she was here, she bragged about how the 3-year old was doing something annoying (licking things like a kid does) and she had to "pop" the kid to get them to stop.My skin crawled when she told it. Fortunately, my husband was on his A game and immediately said "You know, that's normal, small kids have lots of sensory things, they are learning.... our kid does weird stuff, too....." She immediately assured me that our child was "too young to know better" and I left the room.I contacted the mother of the other toddler, sent her a short "no judgement, just wanted to let you know what she said, I'd want to know if I were in this situation" message. I got an angry message back saying they completely trust my mother. Fine.But I can't stop thinking about it.At one point, my husband and I discussed giving my mom a strong boundary: if you ever hit my child, you will never see them again. A friend of mine, however, said that they interact so little, I should let it go and the child will learn on their own that "grandma hits and I don't like that" and the issue will correct itself.Is there a middle ground? Is there a solution I'm not seeing because of my anger? Any advice is appreciated. via /r/Parenting https://ift.tt/2FycUho