Callie,
You can apply methods and tools that can create a neutral zone.
Since she's your children's grandmother, you will have contact with her.
However, any discussion of your EX can be defined as off limits/no response.
You can apply methods that do not allow her direct, real-time access to you, such as she can leave a message on your phone, or email you. Even if you are right there, you do not need to respond directly and in real time to her, until you know what she wants and whether it's in your best interest to engage in it, or not.
The worst case scenario is probably she calls you for a medical emergency of one of your kids. EVEN THEN, you can screen her message, and call her right back.
Sometimes, the only way to win, is not to play.
CLMI