flower girl vs assistant

flower girl and assistant both are nouns.

Word	Noun	Adjective	Verb	Adverb
flower girl	Yes	No	No	No
assistant	Yes	Yes	No	No

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

flower girl: a young girl who carries flowers in a (wedding) procession
assistant: a person who contributes to the fulfillment of a need or furtherance of an effort or purpose

Other hypernyms of flower girl include help, helper, supporter, female child, girl, little girl.

flower girl (noun)	assistant (noun)
a young girl who carries flowers in a (wedding) procession	a person who contributes to the fulfillment of a need or furtherance of an effort or purpose
a woman who sells flowers in the street

flower girl (adjective)	assistant (adjective)
	of or relating to a person who is subordinate to another