Your grandfather's sister is your great aunt. The grandchildren of your great aunt are your second cousins. Their children, the great grandchildren of your great aunt, are your second cousins, once removed.
Your her great great aunt!
Yes, along with your grandfathers' sisters, if any.
Your sister's granddaughter is your great niece and you are her great aunt (if you are a woman) or great uncle (if you are a man).
Great neice
Your great uncle's granddaughter is your second cousin.
Your mothers sisters Granddaughter is your second cousin
Your great grandfather's half-sister is your great great aunt, the same as his full-sister is.
Your her great great aunt!
WHAT relationship* is your Gramps to your great granddaughter? pretty tricky but (distant sisters one off)
You and the granddaughter of your grandmother's brothers, and sisters, are first cousins.
Your nephew's granddaughter is your great great niece. Depending on whether you are male or female, you are that child's great great uncle or great great aunt.
If your great great uncle (the brother of your great grandparent) had a great great granddaughter, you would be third cousins, once removed.