Green’s Dictionary of Slang

(US) a girlfriend.

1992		Proper Dos ‘First Day of School’ 🎵 on Mexican Power [album] Had my jaina crease up my dickies, / Put a close hood on my neck, / So my other jaina wouldn’t see me hickies.
1996		P. Beatty White Boy Shuffle 90: This centrefold jaina del mes is fine.