Let's turn this around.
"I have two lovely medium sized dogs that I can't leave home alone. My son's wife is about to give birth to my son's second child - and of course, as proud granny, I intend to be around there as much as possible, soaking up all the lovely newborn time I can! But my DIL is now saying she doesn't want my dogs in her house, because they track mud all over the place and get up on the furniture and she doesn't like that.
"MN, of course I try to keep the dogs off the furniture, but I'm just one woman. I can't possibly be held accountable for what they do when I need to pop to the loo, can I? I mean, what does she expect me to do, just not use the restroom the whole time I'm there? Spend the whole time telling my lovely doggies off and get no time with the baby?
"Who is BU, me or DIL?"
If you read that, you'd tell her to leave the dogs at home. You'd say "why can't you leave them at home? Because they'll wreck your house? Why is it okay for them to wreck DIL's house but not yours?"
So reading the ACTUAL OP, I'm saying, your house, your rules. Put your foot down - like a PP has said, BEFORE baby is born, while you still have the strength and mental fortitude to do so.
She's had her turn running a household and making the rules. She doesn't run your house, and she doesn't make the rules in your house. If she wants to see the baby, then she needs to make good choices.