Prima
A boy cousin is "primo." A girl cousin is "prima"
prima = cousin who is a girl primo = cousin who is a boy
Yo soy su primo.
Novia (girlfriend) amiga (for a friend who is a girl)
You could use chica or muchacha.
Nieto. If the child is a girl, nieta.
mi primo Nina esta enferma
'La chica se crece' is how you SPELL 'The girl iks growing up' in Spanish 'lah CHEEkah say CRAYthay' ('th' as in 'thin') is how you say/pronounce it.
"tortuga perezosa"
Cousin
In Spanish, a second cousin is called a primo segundo.
"Other girl" in Spanish is "otra niña." It is pronounced, "OH-trah NEEN-yah." Sites such as learn-spanish.co.il provide audio pronunciations of many common Spanish words.