It really gets on my nerves how my MIL almost everyday asks my husband "why didn't you bring the baby"

He goes down there alot because we live in a trailer park and we are five houses down. He will just tell her "come to my house and see him" and she won't. She literally gave him a look the other day when he invited her. Like, isn't it just kinda unfair that she won't ride back with him to see our son, but expects to see him nearly everyday? And our house is clean. There is no reason for her not to. And when our new baby arrives in December, he/she won't be there, period, for a while because she smokes in the house. Does anyone have any insight on why she won't come here? But she has came to eat supper a few times. I don't get it.