Should I call my cousin and tell her to never contact me or my family again?

My grandfather passed away 2 days ago. Many of our family members stopped by the grandparents house to check on my grandmother and pay their respects.

The only person who was not welcome there was my drug addicted cousin who just got out of prison and has robbed my grandparents in the past(along with every member of my family). He showed up, and was very promptly told to get out. He made an absolutely awful comment to my disabled uncle before leaving and really upset my grandmother, who was already grieving her husband of almost 60 years.

After this, my grandmother called the sister of the drug addict cousin just to tell her what had happened, because she didn’t want to cause problems among the rest of the family. The sister of this cousin then went and told my mom and the rest of our family that my grandmother was “ranting and raving” and made up a bunch of lies that my grandmother did not say (the phone call in question was witnessed by multiple people and they all say that my grandmother was nothing but friendly and cordial on the phone) and upset my poor grandmother again. She said that she wants “a drama free life” and would not be attending my grandfathers funeral.

I have been seething with rage, my grandmother is already having the worst week of her life and then to be hurt so badly by people she loves makes me want to scream. I’ve thought about what I would say, and I don’t plan on screaming at her or cursing her out, but I feel like i need to stand up for my grandma.

Any advice?