I would only add that the likeliness of her getting caught hinges on whether she is an independent contractor and owner of her business or an employee. Also how she receives payment for that business.
If she is an employee she's easily busted because all her paycheck dates are documented with the IRS. No audit necessary. If she is an independent contractor it would matter how clients are paying her and who is !099ing her. 1099's don't give dates of when money was paid but paychecks do. If she is a business owner she'd have to be audited to get busted. And maybe not even then.