If your wife has a written employment contract, then it may not be modifiable by the employer without the employee's consent. Likewise, if she has a union, there may be things an employer can't do, and she can ask her rep. If she has neither an employment contract or a union membership, she's an "at will" employee and therefore can be fired without notice at any time for any reason or no reason at all, and she's able to quit without notice and for any reason or no reason. Likewise, the employer can do less than fire her, like demote her and/or reduce her hours or salary.
If she's unwilling to file a complaint about the restrictions on breaks, your wife's only option seems to be looking for another job.
Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.