little girl vs female

little girl and female both are nouns.

Word	Noun	Adjective	Verb	Adverb
little girl	Yes	No	No	No
female	Yes	Yes	No	No

As nouns, female is a hypernym of little girl; that is, female is a word with a broader meaning than little girl:

Other hypernyms of little girl include female person.

little girl (noun)	female (noun)
a youthful female person	an animal that produces gametes (ova) that can be fertilized by male gametes (spermatozoa)
	a person who belongs to the sex that can have babies

little girl (adjective)	female (adjective)
	being the sex (of plant or animal) that produces fertilizable gametes (ova) from which offspring develop
	for or pertaining to or composed of women or girls
	characteristic of or peculiar to a woman