Could the employee in question decide to sue? It's not just Whole Foods he slandered. I'm sure that employee was worried sick about being branded as a bigot.
It's possible, but she will have a problem of proving harm since she wasn't publically identified and the local Whole Foods, and then the corporation itself, was so quick to stand by her that there was almost no time for her to suffer any actual damage. Texas may allow defamation per se claims, meaning she doesn't have to assert a specific injury, but I don't know. She could assert some infliction of emotional distress claim, but those are typically hard to recover for as you have to plead more harm than just that the thing made you upset.
Regardless, she will have to determine whether it is worth it to even get a judgment against this person, as he probably has no means to pay a judgment and may not for a long time, if ever.