Muslimah vs niqaabi

Muslimah and niqaabi both are nouns.

Word	Noun	Adjective	Verb	Adverb
Muslimah	Yes	No	No	No
niqaabi	Yes	No	No	No

As nouns, niqaabi is a hyponym of Muslimah; that is, niqaabi is a word with a more specific, narrower meaning than Muslimah:

Muslimah: a Muslim woman
niqaabi: an observant Muslim woman who covers her face and hands when in public or in the presence of any man outside her immediate family

Muslimah (noun)	niqaabi (noun)
a Muslim woman	an observant Muslim woman who covers her face and hands when in public or in the presence of any man outside her immediate family