So how did it go last night? Likely she has a right to attend events the children are attending or a part of, particularly school events. So if she came, I wouldn't overreact.
Up until this point Mom has basically removed herself from contact. The kids have talked about running away with her.
For this reason I wouldn't agree to letting her have the children on your parenting time. See them in public settings, okay. Take them with her for local dinner or event, maybe but probably not? Overnight, no. Just in case.
I have basically made sure to make every phone call and skype session to Mom happen when she asks. It was only about twice a month. Recently she wants to do a weekly.
I believe her request was due to the looming court hearing or trial, she wanted to show she was an involved mother.