Hi There!
In your post, you stated that your cousin's days of work were cut from a 5-day week to a 4-day week and that her salary would be cut by 20%. My question to you, here, is if your cousin was an exempt or non-exempt employee before the cut, and did her status change after the cut. An employer does not risk "losing" exemption status. However, an employee does, depending on the DoL tests for each category of exemption status.
As far as the holiday concern, if she is considered non-exempt (exempt if there is a supplemental contract), the employer is not required to pay for any holiday the office (or place of business) is closed. If the employer moved the working days from Tuesday - Friday, from Monday - Thursday, he/she is still not legally bound to pay her holiday pay. Salary does not preclude an employer's willingness to pay holidays. An exempt employee will be paid whatever the pay-cycle set amount is based on a per-annum value. A non-exempt employee should be paid a calculated hourly amount based on a per-annum value only for hours worked. If the employer figures in to that schedule holiday pay that's great, but he/she is not required by law to do so.
Hope this helps!
Cheers!
sreising