Great neice
WHAT relationship* is your Gramps to your great granddaughter? pretty tricky but (distant sisters one off)
Your uncle's granddaughter and your child are second cousins.
your niece
You granddaughter is a great great niece of your aunt. Your aunt is your granddaughter's great great aunt.
Your sisters grandson would be your grandnephew.
Your mothers sisters Granddaughter is your second cousin
Your granddaughter and your sister's grandson are second cousins.
Your granddaughter and grand niece are second cousins to each other.
Your great nephew and your granddaughter are second cousins to each other.
Your grand-niece.
Yes
Your son and your sisters child are first cousins. The granddaughter is out of synch by a generation. That will make them first cousins once removed.