Ghosting a friendship?

I have a old best friend from middle school we grew apart and started hanging again about 3 years ago. I’ve always kinda tolerated her because she’s an old friend she’s just a really ignorant person with no manner or common sense. I have a baby now and I have pretty valid reasons to not be friends with her anymore. She’s come to meet my son while her bf was sick twice now and she brought him after I asked her to make sure they weren’t sick because I have to actually ask her since she doesn’t have the common sense. And other little things I just have a hard time being around her especially now. Anyways her wedding is in September and she wanted me to be a bride maid she seems to think we’re really good friends still, I declined but still planned on going to her wedding. We hung out yesterday and I realized I no longer can tolerate her. I feel bad because she was a good friend and she’s a nice person but we have nothing in common and I’m very upset with a few things she’s done. Do I go to her wedding then cut off friendship after? Ghost her or tell her?! I’m so lost. And I don’t normally cut off people but I’ve just been putting up with her for a couple years and now it’s the last straw and I’m over it. The last thing I wanna do is hurt her or do it before the wedding but it’s just who she is it’s nothing she can change. And I feel terrible but I need to make the choice on who’s good to have in mine & my sons life. Tia