muchacha have two meanings, in the first case, the usual, muchacha is "girl", but the second case is when you call a maid, in latin america the maids are not like english maids, usually the "muchachas" or simply "chachas" were girls without education and future in the life, her only purpose were to serve to the landlord and usually the chachas were dirty and didn´t talk spanish very well, and they were like slaves along time ago (XIX century), in some countries the muchacha (maid) is still running, but now is usually to talk muchacha just like a girl.