How do youn handle a two face mother in law?

My mother in law can win an Oscar award. It seems she is the nice good buddy character in the film but she is an interfering *****. She retired only recently and perhaps there is no much to do at home. It is a shame I feel sorry for her because she leaves alone no wonder her character is so appaling. She phones our house and interfere..She visited our house and interfere and even it was a good outing it will be spoiled of her dramatic issues. And now she is trying my mom who is so kind to us to fell out with my husband because of a postcard with my new baby photos and hypernated names. It become like a volcanic eruption when she whispered some "nonsense feed" to my husband' s ear that goes right up his brain. What is the big deal. So upsetting. Especially a nice gesture from my mom... her way for a new baby and a family ties. Please advise. Is she jealouse with my mom? Me? but why?