Wahida
Yes. Wahida is derived from the Arabic root w-h-d and functions as the feminine of Wahid.
The exact name Wahida does not appear as a proper name in the Quran; the root w-h-d occurs in Arabic vocabulary but there is no direct verse citing the name as a person.
Yes. The name has been adopted by some Bengali and Sindhi-speaking Muslim families as an uncommon, poetic feminine name.
Common pronunciations are WA-hee-dah or WA-hi-dah, reflecting Arabic phonology and South Asian adaptation.
Yes. The masculine form is Wahid (وحيد), meaning 'one' or 'unique'.