Those staying with in laws and with helper. How is their relationship? My mil is those traditional type and very hard to get along with. Previous helpers all left becos of her. My r/s with mil isn't that good either and will often quarrel becos of helper. We try not to communicate if possible. Trying to keep my sanity here.

In cases with difficult in-laws, I'd always advocate getting your partner/husband to step in. In my experience, this method will make things easier, less complicated and definitely helpful if you are afraid of being confrontational. Perhaps your husband can spin the situation to your advantage by telling his mother that since he has hired the helper for everyone's benefit, it's only fair that your MIL go easy on the helper and not "scare" them away. Tell her that good helpers are hard to come by and she should TRY to get along with them.