ring girl vs fille

ring girl and fille both are nouns.

Word	Noun	Adjective	Verb	Adverb
ring girl	Yes	No	No	No
fille	Yes	No	No	No

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

ring girl: a young woman who holds up cards indicating the number of the next round at prize fights
fille: a young female

Other hypernyms of ring girl include girl, miss, missy, young lady, young woman.

ring girl (noun)	fille (noun)
a young woman who holds up cards indicating the number of the next round at prize fights	a young female