sesqui-first cousin-niece

Sesqui-first cousin’s daughter.

My sesqui-first cousin-niece is a good girl.

half-first cousin-niece

Half-first cousin's daughter.

My half-first cousin-niece is a good girl.

first step-cousin-niece

1. The granddaughter of one's parent's stepsibling.
2. The stepgranddaughter of one's parent's sibling.
3. The granddaughter of one's stepparent's sibling.

My first step-cousin-niece is a good person.

double-first cousin-niece

Daughter of their maternal first cousin with the paternal first cousin or double-first cousin’s daughter.

My double-first cousin-niece is a good person.