That really sucks that they emailed you like that, Kariann. As someone said, at the very least they could have provided some detail about what they wanted to talk about.
I agree that the email sounds ominous, but it may very well not be the loss of your job. They may just want to know what your plans are, and for you to work with them on transition so the workforce has a minimum of distraction. They may want to talk with you about the other people's comments (what the person said that talked to HR) and make sure that you are treated respectfully when you are are back at work -- again to keep the workforce to a minimum of distraction AND to minimize their liability. HR's first, second, and third job responsibility is to keep the employees productively working. However, they may well choose to do that in a way that actually supports you.
In fact, HR would have to be *seriously* incompetent to send you that email with the intent of firing you. No matter what protections you do or do not have in Ohio, you could still make a whole lot of trouble for them. And I would imagine that the ACLU would take up your case in a heartbeat!
I'd suggest going into the meeting with a positive attitude. You can always change to bitch-mode later, with a lawyer if necessary.
Kim