I feel for you Solobiker. My ex MIL would come stay with us from Europe, not for a month (she would split her time with her daughter), but even a few days would put me in a really bad mood.

It helped me to realize that I could not change or control what she did, but I COULD control my reaction to her. That helped me alot.

A month is a long time. Is there a class or an activity that they could sign up for?