Dealing with sister in-laws!!

Has anyone been in a similar experience where your man has 1 or more sisters.

They are all nice to you when your dating but as soon as your are married it's like a switch has flipped??

My husband is one of five (he is the only male).

Two in particularly are constantly interfering in our life. It's really getting me quite upset.

I've already confronted the 'main' one about why she feels the need to be so nasty to me and behind my back when I have been nothing but kind to all his family.

But nope she is back at it.

Husband says just ignore it don't let it bother you. Yes I wish I could but when it comes to affecting my little family I don't want to allow that.

Any ladies have similar experiences??