Mom moving away and I don't care

Okay, too many years of problems to unburden it all but I'll try to summarize what has led to this newest... adventure?

My sister has a son who has an unhealthy interest in my youngest. They are five years apart. He has been hyper-fixated since they met, she was 2 and he was 7. The older two sit next to her at family dinners to block him from contact, he touches her when she says no, throws things at her, etc. We've brought it up in the past, but my sister doesn't handle criticism of him well due to his other parents' being bad parents. Things came to a head when he turned 18, and she was 13, still focused on her. It ticked us off because our hands felt tied.

Now, my husband and I had been married for almost 20 years at that point. He has always dropped everything to help my mom whenever she's needed anything. Has driven her to doctor appointments, took off days to move her into her new home after the divorce and did any repairs she needed, rescued her from situations she got herself into, would randomly drop off treats to make her day better, helped her get a job, etc.

In the middle of our growing frustration over my sister's situation, I was supposed to take my mom to an appointment but had a seizure and couldn't drive her. My husband was stressed because it was the middle of a work day, I wasn't doing well at all, and he's angry about not being able to do more to protect our kid. My mom took an edible, which she has admitted may have impacted her perspective, but she asked him to open up to her about the situation. He vented, getting loud and passionate, and my mom (again by her admission) kept encouraging him to speak, telling him she appreciated he trusted her.

When she got home, she called me and was upset because she felt threatened and was too scared to say anything. She didn't ask him to stop speaking, didn't change the topic, just asked him to keep talking with her and told him how glad she was he trusted her. He didn't even know she was upset.

Then she shared what he told her with my sister which blew us up. I can't be mad at her because she was protecting her kid in her eyes, but I'm protecting mine too, and just don't want him at every event the kids have or want him around the girls when they hang with her. We can tolerate doing our protective measures at family get-togethers but the kids shouldn't fear that they'll have to protect the youngest at their concerts, and other similar events.

It continued. My mom took our middle to my middle's place of work and very loudly, heavy swear words and all, bad-talked us, dropped the whole situation on her, and then told her not to tell us they spoke about it. My kid was humiliated, hurt, and put in an uncomfortable place of break our trust or break grandma's trust.

This is a conversation I've had multiple times with my mom. Just because the kids share secrets with her doesn't mean it's appropriate to expect the kids to hide her secrets. She doesn't get it and punishes them when they spill the beans. Anytime she speaks to them afterward, she tells them that she wants to talk to them, but can't cause they'll just tell their parents, and makes it so miserable they don't want to be around her.

This was the breaking point for me. She's done her fair share of manipulation, mental abuse, crossing boundaries, over 4 decades to me, but hurting my family in such an aggressive manner broke me. I decided I was done and told her as much. So's my husband. The kids are old enough I didn't cut them off from her but allowed them to choose to continue their relationship but wouldn't force them too if they weren't comfortable.

Over the last year, she's continued to do crappy things to them. Making and canceling birthday plans, her birthday gift to the middle was items she found in her junk drawer she didn't want or didn't fit her, oversharing her private life (think men), punished them if she thought they didn't interact with her often enough.

And then, the cherry on top, she got engaged to a convicted child molester of his own daughter who is only a few years older than me that she only dated online. She was going to move to another state with him. Then she went and hung out with him for a week, nearly missing the birthday plans she made with the oldest, and decided that wasn't going to work out cause he was abusive and crazy.

The kids had enough. The two younger ones have gone NC and the oldest is on LC.

A couple weeks ago, she let me know she is moving to the other state. I didn't know how to respond. I told her okay, stay safe, and love her back. But I can't give her more than that. I don't care anymore. My sister and she have told the kids that they think she has bipolar disorder so it's not her fault and she's going to get therapy, but it feels like too little, too late. I would love if she could find a way to get better but I'm just not wiling to put myself or my family in her firing line anymore.

Her moving is a relief. While she's near me, even as much as I love/hate her, if she needed help, I would give it to her. But when she's on the other side of the country, she's made the choice to isolate herself and I don't have the capability to get to her. It puts it in the hands of my sister who would be able to reach her and I'm not gonna lie, that is such a weight off my shoulders.

UPDATE: She fought with the people she was moving out to, and now she didn't leave. And that's how I expected it to go.