Manipulative MIL

My MIL is very controlling and manipulative. My husband is so devoted to her and cannot see anything wrong in what she does. She always tries to manipulate him into doing what she likes and wants. Recently my husband said he wanted to grow a beard and I was okay with it. She saw his beard in a pic and started throwing a tantrum. She cried saying that she doesn’t want her son to have a beard and that her friends/relatives would think less of him if he is not clean shaven. This has been going on for a couple of days now and she has given a deadline that he must be shaved by this weekend. I feel that it is so wrong that she is trying to control a grown up adult man like this. My husband being him promised her he will remove his beard. I am just so pissed with both of them. Should i forget this as something between mother n son or are they both wrong.