Question

A religious employer and a religious female employee would like her to work two hours a day in order to provide customer service to people who purchased in the past. Delaying the service until after the holiday would seemingly be considered a case of financial loss.
Is it permitted for the employee to work a minimal amount, and instead of an hourly wage to give her the pay as a bonus—that is, the hours worked on Hol HaMoed would not be recorded?
If she did work, is the transgression only on the employee, or also on the employer? And if she did work, is the employer permitted / obligated to pay her?