MIL will be bringing 16 year olds foster child when I’m about to give birth.

I want to start off by saying I love my MIL, but so much has happened recently. After being a Christian for her entire life she recently took in a foster child (M16) and converted to his native religion, Islam. I have never met him. I was already feeling a little iffy if my BIL might be coming, and I assumed my MIL would be coming with her cousin and splitting a hotel, but just today she asked how big our couch was and if her foster son could use our eldest sons room. I feel like this is a very colleague time for me and I don’t want to be rude, but I really don’t want this kid so I’ve never met to be around when I’m possibly in labor and then breastfeeding and exhausted afterward. I’m autistic and have sensory processing disorder and many times I prefer going around with just my nightshirt/gown and honestly I’ll just be in a really vulnerable position at this time. My husband said he will talk to her if I can help think of something to say. Edit to add context on modesty and why I mentioned religion. I copied from a comment I made below: I mentioned it (religion) because the foster child is not from the USA and the Islamic religion has strict regulations on modesty and such and foster child may be seeing me half naked if he stays here. It’s more about the religious aspect of modesty but I’m also LDS and we also take pride in modesty, it’s more that I don’t want a stranger seeing me half naked over the first few weeks post partum. Due to being autistic and SPD, I have a hard time wearing “modest” clothing especially when uncomfortable/ in a lot of pain or healing.