Recently, I found out my cousin has been stalking my ex (daughter's father) on social media and showing people in my family his new girl friend & their new child. I'm so angry, she has no connection to him AT ALL and has no right to be showing people in my family this. She showed this to her brother & he went off and started telling my daughter about her baby sister, when that's a talk that I haven't brought up to her yet (her dad is out of the picture) they've crossed boundaries and I don't understand why my cousin feels the need to look into my past & bring it up.. especially look up my ex on social media then tell everyone what he's up to.

My mom told me that my cousin has been doing this for a while and has even commented on how my daughter's step sister is sooo pretty, even prettier than my daughter.

I'm so upset, I want to completely cut them off (no contact) I've talked this over with my mom but she thinks "I'm overreacting" and that "I need to forgive them" I dont think I am. What would you do in this situation? Am I being too harsh?

Edit;

His profile is on private, she requested to follow him.