I think this is about actions more than speech. Essentially, she hazed him. If she’d been his pledgemaster or his drill sergeant, she’d be in trouble, because she did things that are specifically outlawed because they have been used in hazing previously, found to be too cruel, and been done away with.
In a civil court where the family tried to recover damages, that would probably be a very effective argument, but not in a criminal court, because I doubt there were any actual criminal laws she violated. Hazing is against a lot of policies, and can get you kicked out of college, or given a UCMJ in the military, but I doubt that Dairy Queen has a policy against hazing. It probably has one against harassment, and that’s why she’s been fired. The family may not have a case against DQ itself, though, if the victim never reported the harassment. DQ upper management can’t intervene, if it knows nothing.