It could be anything that set her off. She sounds like her suspicions and paranoia ... . and emotions... . have got the best of her. Not a pretty place. This is difficult to contend with.
Taking care of you and your children is important. Something that may help (because you have to have contact with her) is establishing a plan and some ground rules for yourself in regards to the who, what, how, when, where and why of talking with her.
You're gonna need some value based boundaries and some tools here. Approaching it the same way as before ain't working and you said
3 hours later and I feel like dying just so I never have to fell like this again
Here's the primer on Boundaries:
https://bpdfamily.com/content/values-and-boundaries Part of detaching from this is Step 4 Creative Action... . so let's get creative here and develop a plan for interacting with her that is healthy for you and your kids.
