I do not want sil at ds first birthday because:
1. She is a dirty slut and I dont want her or her druggo boyfriend around my son or at my house (sil is the town bike no joke, I cant go to the local shopping centre because I have all these random guys coming up to me asking if I am her sil and then they tell me they have slept with her and I receive atleast one nude photo of her a month from guys she has slept with. I still dont know how they are getting my number)
2. They will try and make ds's day all about them
3. She would have a about 3 week old baby, who I dont want getting sick (there is going to be alot of kids at the party and its not the babys fault she has a horrible mother who would rather be selfish than keep her baby well). I do not want mil thinking she can just invite sil. Mil knows I hate sil and I had made it very clear I dont want anything to do with her, I know thats going to be super unfair on our kids but I just dont trust sil at all! So how do I deal with the 'why isnt sil invited?'
Oh and mil makes cakes, they look great but dont taste so great and my nanna wants to help out a friend who is starting a cake business and is going to pay her friend to make the cake for ds. How do tell mil she isnt making the cake? (She thinks she is making the cake, I didnt ask her to though)
What does your husband think about this? Has she had a big part in your childs life? If she hasn't shown an interest chances are that she wont come anyway.
I would just be honest about the cake and say you already have it organised.
I never stayed home because I had a newborn, I don't think your SIL should have to miss the party because she has a new baby, I think you are just trying to come up with excuses with that. When I had DD3 in November we took her to the kids school at 5 days old.
I think if you really don't want her there then you need to talk to her and explain it to her, be honest with her.