Am I right to be mad?

Let me start by saying my SO mother never really liked me shed called me a whore ( I was a Virgin till her son) and a devil worshiping witch since I don't claim to have a religion and that I had a "spell" on my SO because he was taught class and wouldn't think twice about of me and would talk and hangout with my SO ex to talk about us and because she was the daughter she never had. It wasn't until after I had her first grandchild that she was decent with me  but even then she would bring up my So ex and talk about how she was the one who got him through college and kept him on track and ect. She's even called me her name multiply times . I looked past it and just said it's not about her it's about my SO and I and our son. Well today my son (who's 13 months) had her iPad  (she left it with him when she came over) and accidentally went to her emails so I quickly took it away so he couldn't delete anything, well I found these emails that my SO mother and my SO ex talking about how she wanted him to wait and tried to convince him not to have the baby but that she loves him. And how she doesn't think he's ready to marry anyone yet. And basically made me out to be just the person who had her grandson. She went on about how she missed her and would love to see her.  My SO and I are so angry because it wasn't like they broke up a month ago.. They broke up 3 YEARS AGO.  We don't understand why she can't just stay in the past.  I don't know know how to bring this up but I feel as if I need to because really hurt my feelings since I've worked my a@@ off trying to get along and finally though she liked me. Plus I know she wouldn't say sorry since she never said sorry before for calling me all those horrible names before.