You and your mother's niece are first cousins to each other, so your and the niece's daughter are fist cousins, once removed.
Your niece is the daughter of your brother or sister. That relationship is not ended by divorce. If your brother married a woman who already had a daughter (from an earlier marriage), then she would be your "step-niece", and this relationship would, technically, be ended by a later divorce.
The relationship to you would be your cousin !
Grand niece.
Your niece's daughter is your great niece. You are her great aunt or great uncle, depending on your sex.
You are their aunt or aunt by marriage.
my cousons sisters boyfriens dads nieces grandma's favorite sons dogwalkers mothers friends mum twice removed uncles daughter
Great-niece.
your 2nd niece...!
Your daughter and your niece's child are 1st cousins once removed.
Daughter hates mothers should she send mothers day card to daughter
My niece's daughter is my great niece.
You are her grand uncle (or great aunt) and she is your grand niece.