According to a post on her facebook page (via Trek Core on twitter), she was taken to the hospital after a mild stroke, and they're doing tests to see how severe it is. George Takei has also tweeted that she was hospitalized.
I got to see her in person at the anniversary gala at the Science Fiction Museum in Seattle a few years ago, and she was amazing to listen to. I've been following her on twitter since, and I've been worried that nothing's come over her feed for a while.
Last night Nichelle Nichols had a mild stroke. The Steel City Con has been updated by her representative that “Nichelle is awake, eating, in good spirits and able to have full conversations.” We know many of you are excited to meet Nichelle at the upcoming show and we will continue to give you updates. In the meantime please keep Nichelle in your thoughts and prayers.