Son keeps getting sick at MIL's house 🙄

So, my 3 year old visits his paternal grandma once in awhile & every time he comes back from her house he is sick throwing up or sick in some way, I've tried to stop him from going so much, but she comes and basically guilts me into taking him which bugs me because my SO doesn't say anything about it, so ladies what should I do in this situation? She took my son this Sunday he was sick throwing up constantly at her house and she didn't even let me know she took him to the doctor and what was even going on till she dropped him off she didn't even tell her son he had no idea either I'm at my wits end 😤 also her house is really dirty she's sick so she rarely cleans and she has a lot of little dogs I try to keep him home but she bitches till she gets her way 😒