Employee signed up with MetLife for long-term disability through Sears Holdings Corporation. Employee contracted cancer of the breast during employment at Sears.

Fast forward: After 5+ major operations to remove cancer from employer's body, employer discovered that she was receiving $500+ less in benefits from MetLife. Apparently, MetLife, although aware of the discrepency in income submitted by former employer and IRS income tax filings, which confirmed the employee's earnings; MetLife refuses to reimburse employee o of over $30, 000 in benefits from 2007 to present.
Any suggestions on the best course of action to take against MetLife, etc.?