Yes. That is exactly what she is telling you.
While you cannot be fired BECAUSE you filed a workers comp claim, you CAN be fired because you are unavailable to work EVEN IF the injury was a workers comp claim. In this instance, the ONLY law that would have protected you from being let go was FMLA. If FMLA did not apply, they could have fired you more or less immediately. If FMLA did apply, they only had to hold your job for the equivalent of 12 weeks. Since they held it much longer than that, you can legally be let go, regardless of FMLA, regardless of w/c, if you are still unable to return to full duty.
No employer in any state is required by law to hold an employee's job or keep them on light duty indefinitely. Eventually, the law is going to allow the employer to cut the employee loose. Yours kept you on longer than required by law.