Venting! Who would bring a sick baby to a babysitters house that has other babies there for them to get sick? My M-I-L…

Venting! Who would bring a sick baby to a babysitters house that has other babies there for them to get sick? My M-I-L watches my daughter (4 months old) while me and my husband works. Well my husbands cousin has a 5 month old that supposedly was sick and now she is sick with a cold. Well she started bringing her baby to my M-I-L's for her to watch and now my baby is getting sick!!!! I am beyond pissed!! If she and her baby is sick, why bring him over where he can get my child sick? She could has left her child at the other babysitters house until he get better but NOOOO she had to bring him over there to get my daughter sick!!! 😡😡😡