Upsetting mom

So a little while ago, I had made a post about whether or not I should invite my grandmother (mom's mom). Here are the highlights:
When she first met FH, she was extremely rude to him and started talking about other guys that she was going to introduce me to instead. 2nd time meeting him was at a public dinner, she got into a huge argument with him about how wrong it was for me to have even seen his apartment (she's extremely religious). Any time he was brought up in conversation, whether he was there or not, she would start making snide comments and would just be awful about it. When we moved in together, she started shoving bible verses down my throat and was telling me that we both would end up in hell. I could go on, but for the sake of long posts, I'll stop there.
I decided not to invite her. I felt as if she couldn't support our relationship and was trying to break us up from the beginning. I discussed this with my mom who was saddened, but seemed to understand that I had to do what I had to do. So I wrote a letter to my grandmother explaining how she hurt me and why I didn't want her to attend the wedding. She wrote a letter back a couple months later apologizing and asking for forgiveness. I have not responded. I'm at the point where I want to forgive her, but I'm not even close to ready to invite her back in my life. I don't want her at the wedding. I don't want to see her. I understand she's my grandmother, but she's the most toxic person to ever be in my life. She has never supported any of my decisions, especially when it came to FH. So why would I want her there to celebrate my decision to be with him for the rest of my life?
We are now less than 5 weeks away, and my mom has decided that she really wants her there, no matter what she did to me. One of my mom's friends who I adore is coming to the wedding. She has offered to play interference with my grandmother so that I will have little contact with her. My mom is really pushing every angle she can to have me invite her. It came up in a group conversation the other night that I had made up my mind. I did not want her there. FHs whole family is also worried about her being there because of how judgemental she is, and they are all covered in tattoos, and they enjoy the occasional alcohol. My mom is so upset that I won't invite her, but she is still pushing. I don't know what to do. I really don't want her there, but my mom really does.