It is my understanding that at least in Texas it is illegal to give out the information that she gave you.
It is my understanding (IANAL) that it's not per se illegal, but that it could open you up to a potential lawsuit. That's why some employers, when asked for a reference, say nothing more than to verify dates of employment, job title and salary.
A lot of companies, including 7-11 according to the article, therefore have a blanket policy of making no public statements on personnel matters. If they made an exception in this case, my guess is that they felt the bad PR outweighed the lawsuit risk.