No, if your wife can use FMLA (the company is large enough to be covered and she has worked there long enough and enough hours; you can find the FMLA eligibility criteria on the U.S. Dept. of Labor or DOL website), then she has an absolute right to use it for medical care and the company can neither deny her the time off nor retaliate against her for using FMLA leave then. If they try to do so, she could file a complaint with the Dept. of Labor and/or look to bring a lawsuit.