Green’s Dictionary of Slang

(US) an attractive young woman.

1973		oral testimony in Lighter HDAS II.
1981		J. Stiehm Bring Men and Women 257: One male cadet...mistakenly hallooed a woman officer as a ‘fucking mamacita’ [HDAS].
1986		Miami Vice [NBC-TV] Hey, mamacita! [HDAS].
1994		Nat. Comms. Assoc. (US) Communication Monographs 262: Mamacita constituted a key element in the verbal applause that follows young women [...] directed at them by men with whom they are not acquainted.