No. That is illegal. The employer can not withhold wages earned. If your mother worked time she is entitled to the wages for that time worked regardless of any other aspect of the situation.
If the employer refuses to pay and your mother leaves she would certainly have grounds for a small claims lawsuit to retrieve the wages due to her. Small claims court is set up so that individuals can file lawsuits without paying for an attorney and she would appear to have excellent grounds for such a lawsuit if he refuses to pay her. If it comes to that, your mother can contact the local clerk of courts for information on filing a small claims lawsuit.
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