Mother Threatening To Sue For Grandparent Rights

Hello, I live in MA where grandparent rights are a thing, but has extremely strict guidelines. My husband and two children lived with my mother and her husband. We lived there so I could take care of , she is physically disabled and her husband no longer has his license as he has multiple DUI’S . What happened was her husband got black out drunk, attacked my husband who was holding our children. Cops called, charges are being pressed and we left with a restraining order in place against him since they let him out until his court date. My mother was on our side but then she wasn’t. She wanted us to drop the charges because he was drunk and made a mistake. Yeah, not happening. At first she was allowed to see our children. But then our oldest daughter who is 6 was telling us that her grandmother kept saying we were wrong for sending her grandfather to jail and that people make mistakes. Our daughter told us how uncomfortable she was and that it hurt her feeling that her grandmother kept saying these things. She asked to not see her. I completely agreed. Now my mom didn’t take it likely, threating to call DCF to have them take away our children, telling them we beat them, that my husband is abusing me and the children’s. She actually did call and nothing came of it because I had the text message to prove what she stated. Now she has sent me a letter stating that either I let her see them or she will be taking my husband and I to court to get grandparent visitations. I am almost 100% certain that she has no case here. Her husband is back to living with her while he stands trail, I have many many threating texts messages about her calling DCF, the actual DCF report and it being closed. Not including her husband has been chargers with 2 counts of child as well as a restraining order placed against him.