Singer/songwriter/multi-instrumentalist/producer Elisa Jordana has come a long way since her days as “one of those troubled girls with a guitar writing sad songs.” As “Nymphomaniac” – her down ’n’ dirty reinvention of the Flashdance chestnut “Maniac” – attests, the girl’s developed some genuine joie de vivre and a wickedly delicious sense of humor.She wields the latter to excellent effect in the frequently downloaded “Unstable,” a not-so-thinly veiled recollection of her days playing keytar in the dance-rock outfit Cobra Starship, with whom she toured extensively.