I'm labeled the trigger-tongue from London,'' says Monie Love, a 20-year-old rapper whose first album, Down to Earth, has already put ''Monie in the Middle'' at the top of the rap charts. Born in England to West Indian parents, Love first made a splash in the U.S. earlier this year with some high-velocity guest verbiage on Queen Latifah's hit single ''Ladies First.'' She auditioned for that job while hosting a music cruise on a boat off the coast of England. ''Latifah heard me in the changing room,'' Love remembers. ''The boat was rocking and I was really scared.'' Since then, she has worked with two other American rap acts known for their mellow, Afrocentric pop: Jungle Brothers and De La Soul. While she seems entirely fresh-faced and unaffected, Love isn't afraid to take gambles. She's just moved from London to Queens, N.Y., that stronghold of rap, to be part of its thriving scene. All these changes in her life are a little dazzling to Love, who was training to be a schoolteacher three years ago and has a remarkably modest view of her ability. ''I can't sing,'' she says. ''If I could sing, why, I wouldn't be in rap.''