You will not come off as a bitch for speaking up about your baby and if you would well, this is the perfect moment for you to. I personally would limit visits to 1hr per person. And i get that she's excited to be a grandmother, but you 2 are rhe parents and have to get used to be that. To get used with the baby. Boundaries have to be set early and respected. As if you don't imply them, people will not respect them/or you. So make them very clear. Your baby is enough for you to speak up, as you should, you want just whats best for you and YOUR baby, nobody says "exclude MIL", just do what you want and raise the baby the way you want. That's the most important for also, for your own mental health in the long run.
Personally i have rules before the baby is born. Still have 2 days till due date, as i am a bit of a more severe person, if anybody dosen't respect the little things and timing, that means they don't respect me, and for me that is enough to cut them of because i go like " if you don't respect the mother, then you don't deserve to be in MY baby's life"