I'll admit, it was advice like yours that baffled me when I was on these boards, posting and in crises. I think there's a degree of compassion that everyone her deserves.
Anger is useful in many situations. Obviously, what we do with it is important, but it is a teacher. May, what is it teaching you? What is it here to tell you? There's a book called the Language of Emotions that you may want to get to look at it about this important emotion.
May is clearly acting out of a place of fear and lack. What is the fear? What do you imagine is being taken away or that has been taken or that you don't have?
There's a sense you've given your power away here - to this woman, to your husband. That can leave you feeling helpless, angry, out of control, desperate. It would leave anyone feeling that way. So have some compassion for yourself, and see if you can slow down in all this and find some answers, within ... you do have the power.