Am i wrong and heartless?

so long story short I have a step mom that treated me like shit when I lived with my dad for no reason. I got good grades, had a job and at one point two jobs, was respectful, came home on time, etc. I stayed out of her way and spent my life in my room to try and avoid her.  my dad worked over 60 hours a week so he never saw it or believed me.                                                            well now I've been moved out for about 4 years, I don't ask them for money ever or have them help me out. I caught her doing shady things to my son who is 1.5 so I cut back on how many times I let her watch him because she would constantly beg to see him for some reason. (she never had kids of her own so I'm assuming she just liked playing "mom"). now I'm 9 months pregnant and have appointments all the time so I asked her to watch my son just quick  while I went to it. when I got back i walked in on her sleeping on the couch at noon, my son was screaming and  crying so loud you could hear it from outside, and when I went to go get him out of the room he was put in with the door closed, he was sitting in a very poopy diaper and a mess with puffy eyes he could barely open and snot everywhere. I just grabbed him and got the hell out of there.                                           my fiancé and I decided she would no longer watch him when I go into labor and we will have his family watch him. I also decided to tell her I want my kids to call her by her name, not grandma. after how she treated me for no reason and after that incident, I just can't fake it for my dad. I dont consider her family. she's just the woman married to my dad. am I wrong for wanting her to be called by her name, not grandma?? She literally made my life so bad I attempted suicide twice and was extremely depressed  when i lived with them and I'm constantly worried she's treating my kids bad when no one is around.