Its about control, she is trying to control you and your actions by using the kids. When I started detaching the W HATED it ... she blew up my phone one morning, TM and calls ... then I get a TM "We got into an accident please call" I immediately called and asked if they were ok, she started in on me ... I stopped her and told her it was obvious there was no emergency, no crash, I had no desire to speak with her .... told her to think about what she just did becuase next time when there actually might be a real emergency it will not be my fault for not responding to her cyring wolf game.
When we set boundaries .. they WILL test them
I would simply TM back asking her if there was an emergency you are more than available .. otherwise do not expect a rapid response as you now have a new life (not one you asked for) and will do the best you can to move on.