Your grandniece and your daughter are first cousins, once removed, to each other.
Your grandniece's daughter is your great-grandniece.
Great grandniece
She is his great grandniece.
your 2nd niece...!
You would just be a friend
Your grandniece is the granddaughter of your brother or sister, and the daughter of your niece or nephew. Your grandnephew is the grandson of your brother or sister, and the son of your niece or nephew.
your 2nd niece...!
Your husband's grandniece is your grandniece-in-law.
She would be your Great/ Grand Niece. Seeing as you are her Great Aunt or Uncle.
You are your grandniece's greataunt or greatuncle. Your grandneice may call you her greataunt, or if close to you, may call you simply aunt (or uncle).
Your grandchildren and your grandniece are second cousins to each other..
You are her grand uncle (or great aunt) and she is your grand niece.