ANSWER:

You don’t have to take her permission nor even inform her because she has no right, none whatsoever over you.

What matters is your husband’s permission, if he’s OK with you going then go ahead without waiting for anyone else’s approval. 

QUESTION: My mother in law doesn’t allow me to go to my mother’s home,she says what is the need to go again and again she only allows me 2 days a month but my husband doesn’t have any problem he allows me but his mother is shouting on him because she says without my permission you shouldn’t allow her and he can’t argue with his mother in this case I’m confused what to do