Theory of Quasi Contract

Anthony Maglica and Claire Halasz lived together and held themselves out as a married couple. They acted as companions toward each other. Claire changed her last name to Maglica, even though the couple never married. Together they worked in a business owned solely by Anthony, although Claire participated in the substantial part in the work. The two were paid equal salaries. The company, Mag Instruments, was incorporated in 1974 and all shares went to Anthony. After the company began manufacturing flashlights, the company grew rapidly, exceeding hundreds of millions of dollars in net worth. In 1992, Claire and Anthony separated and subsequently Claire filed suit against Anthony for breach of contract and claimed damages under a theory of Quasi Contract. No contract existed between Anthony and Claire.

Does Claire have any remedy under a theory of Quasi Contract? If so, what must she prove?