The Arabic word which seems the common basis for all of these words is hijab (al-hijab الحجاب).
hijabi in first place doesn't sound Arabic unless it is meant as
but in that case it should be pronounced like hijaabee with a prolonged "a" ا (alif الف) in the middle and "e" (sound of the kasra بِي diacritic which is taken from the letter ba' باء to the letter ya' ياء) at the end.
If it is used as an adjective like:
hijab-u l-mar'ah (the scarf of a/the woman)
Then the use is rather wrong in the fasih (standard) language, however in some Arabic slangs or dialects people may call a girl hijabiyah حِجَابِيَّة (instead of muhajjabah or muhtajibah) which may include both mockery or a respectful attitude depending on the context and dialect, however the first could be the major case.
The most correct Arabic word describing a women wearing hijab is:
- muhtajiba(h) مُحْتَجٍبَة which means a woman who hides or wears a veil/scarf.
muhajjaba(h) مُحَجَّبَة is also used to describe a veiled woman (wearing hijab or hidden behind a hijab/veil).
muhajjiba(h) مُحَجَّبَة would mean the one who puts a veil/barrier between her and others!
There's also the word muhtajaba(h) مُحْتَجَبَة which i would tend to understand as a rather timid woman who hides her self because of fear.