So yep, OP, sorry for the abuse from the resident loons.
These are the simple facts which can't be argued with.
You have very, very kindly granted your daughter the enormous favour of living in YOUR home with your grandchild.
So, of course, you MUST NOT be dictated to as to what you do in YOUR own home, particularly when it is so absolutely normal, standard and completely acceptable as your son visiting and not whispering or creeping around.
She'll just have to deal with it. Nobody normal asks people to creep around in their own home after 7pm 😅
You're already playing favourites by allowing her to live with you, don't favouritise her even more at the cost of your relationship with your son.
You can ask him to keep it down a bit sure, and if he can, great. And if he can't, such is life.
She sounds entitled, super anxious and you CANNOT and MUST not let her start dictating your life to you. Again, particularly as your behaviour and your son's behaviour is so absolutely nothing, normal and uncontroversial.
And your updates have made it clear she even expects YOU to creep around in your home own after 7pm!
As it's YOUR HOME and not your daughter's, she can always leave if people doing normal, basic, uncontroversial things is too much for her.
And she'll be in for a very rude shock indeed if she thinks she can impose silence on people anywhere else that's for sure.
Sorry people have been abusing you OP, there are some genuine nutters on this site.