At your wedding, you are introduced to your new partner’s mother’s only sister’s husband’s sister in law.
What do you call this woman?
I think it should be mother-in-law.
IT SHOULD BE MY MOTHER IN LAW
Mary's husband's father-in-law is Mary's husband's brother's mother-in-law, and Mary's sister-in-law is Mary's brother's stepmother.
How did this happen?