Demi Lovato said "yes" to her boyfriend's romantic beach proposal, and she's gushing that she's finally found a "partner." The "I Love Me" singer's BF, actor Max Ehrich, is now her fiance ... about 4 months after we all found out they were dating. Max popped the question on the sand in Malibu, and he came well-prepared ... with some major bling for her finger.