It's never really clear what she can and can't sense. In the manga, she senses that the Amazon Quartet are improperly awoken and if they don't get help they'll die (and the implication is by her hand). She also knows and even has visions of Usagi getting hurt and even possibly dying thus spurring her to action. She was also uneasy around Kaori but in all cases sans Quartet she doesn't know WHAT exactly is causing them to be sick/make her uneasy. So it's more of a "shit will go down/something is up but I don't know what."