Technically there is no relationship. When introducing her, you would refer to her as My daughter's mother-in-law.
I call her Jane. There is no special name for a person in that relationship.
Your mother-in-law's brother and his children are not related to you.He is your childrens' uncle and his children are first cousins to your children.
The sister of your mother-in-law and her children are not related to you.She is your children's aunt and her children are first cousins to your children.
She is the co-mother in law of you and your daughter's father in law is your co father in law. :-)
I would just call her my second mother
I have most commonly heard a brother-in-law's mother being referred to as a "mother-in-law"
If your brother-in-law is the brother of your wife then his mother is your mother-in-law. If your brother-in-law is the husband of your sister, his mother is not related to you but is your sister's mother-in-law.
Your aunts' mother-in-law.
Daughter
No relation ..
Taresa is either your mother or mother-in-law. Taresa's daughter is either you or your wife.