Mother in law volatility

I am having such a difficult time dealing with my mother in law. One week she is calling to say how wonderful we are and sending a card. The next, some expectation has been unmet and she is passive aggressive. She is silent, short on the phone and makes nasty comments. She will not answer questions asking why she is upset directly. It is eating me up as her inconsistent/volatile behaviour makes me feel on egg shells wondering what I will be dealing with. They installed shelves in our cottage despite us asking them not to decorate on our behalf. When my husband confronted her, we got an email that she was so hurt, she and her spouse were going to hold each other close and take the time to heal. It was quite dramatic and honestly, seemed quite immature.

Treat your mother in law the way your treat an immature child. Accept that you are the most grown up person in this relation.