No...not an uberbitch! (LOL, I've never heard that one!)
I understand your not wanting everyone to get sick...
...but...
He =IS= family. And family has to stick together whether sick or not. It was inconsiderate of his mother to send him over like that
. But once he's there, and he's sick, he needs to feel like he is where he is wanted, and he needs some TLC.
I think you're really just fed up with his mother, and I can understand that. But, you don't want your feelings toward her to rub off on him.
Your husband is in an awkward position too. It is his son. He loves him. His baby is sick, and he probably wants what is best for him. I'm sure it doesn't feel right to send his sick son away.
So, put on a pot of chicken soup, and stock up on kleenex.
This too shall pass.
hth,