That cannot happen.
Your grandmother's sister is your great aunt
Your great grandmother's sister is your great-great-aunt.
Your grandmother's sister is your great aunt.
Your grandmother's sister is your great aunt.
A great great aunt is the sister of your great grandmother. (A great aunt would be the sister of your grandmother.)
Your grandmother's sister is your great aunt.
Your grandmother's sister is your great aunt. Your grandmother's sister's daughter is your first cousin, once removed. (Your grandmother's sister's daughter and your mother or father are first cousins, and going one more generation to you on only one side is the "once removed" part.)
Your mother's mother is your grandmother. Your grandmother's sister is your great aunt, and your mother's aunt.
Yes, your great grandmother's sister is your great-great aunt. Your great aunt is your grandmother's sister.
Your mother's sister is your aunt. Your mother's mother is your grandmother.
Your grandmother's sister is your great aunt. Your great aunt's daughter is your first cousin, once removed.
Your grandmother's sister is your great-aunt.