I was only on sporadically when the diseases were running around and of course my HA got sick. I thought it would go away on it's own when the event ended but that hasn't happened. Can someone PLEASE tell me how to get her cleaned up? I'd really appreciate it. Thanks.

You'll need 50 candy hearts & a potion that was created during the event (example: Blue Liquid-Filled Rounded Flask). You'll then need to visit Louis L'Amour to create your cure.

OR

If you want to skip all that, you can buy your cure (Bottled Antilovirus) from a user shop.