She ran a business selling alien artifacts and artwork on Earth. When the quarantine was put in place after the release of the Drakh plague, she was unable to continue to operate. She was unable to take out a loan, so she took 50,000 credits from Rolf Muller with 100% interest compounded every 6 months. After she made the deal with Muller, she was followed by him wherever she went.
During the month of July in 2267, Cynthia Allen and Max agreed to meet each other on Babylon 5. Max agreed to pay the initial 50,000 credits back to Muller. After giving Muller 50,000 credits, Cynthia's cat was kidnapped back home under the nose of Diane and an ultimatum was given to repay the additional 50,000. Max eventually threatened Muller and used alien technology he recovered from a dig to blackmail him, and the debt was settled.