SHE TOOK YOUR DOG OUT OF YOUR ROOM ,TOOK AWAY HIS FOOD AND THEN SPANKED HIM?!!!
I would tell her post haste not to ever do that again.
you should never spank a dog and a small dog at that. she could break something or damage his hip their little bones are so fragile (would she also so freely pay for any damage she caused him)
I am so mad
and I cannot say any of the things I really want to say.
you have to let her know this is not acceptable in any form and you will not tolerate her abuse to YOUR pup.
she could have quite possibly already cause a regression in his potty training.