It does happen from time to time that hosts don't hear back from guest after contacting them -- sometimes this is because the guest is traveling and has no internet access, so that possibility should be considered. Have you tried phoning the guest as well? /
It may help to focus on what your concern is, and just what you need from the guest at this point. You say that you weren't as careful vetting her as you should have been. Can you elaborate? You say the guest has no reviews -- actually that is very common, and will be the case for any new user of AIrbnb. If hosts never accepted anyone who had no reviews, the whole system wouldn't work, as no new guest would ever be accepted anywhere. Rather than rely on past reviews, it is good for hosts to come up with a list of questions and a method of screening guests, since there will be many guests who have no reviews.
What specifically is your concern now? You say you have a bad feeling, but I wonder, is that solely related to the fact that you haven't heard from the guest, or are there other concerns? What were you trying to convey in the email you sent to the guest (eg what was the purpose for you sending an email)_, and what information do you need from the guest at this point. I would suggest you try calling the guest on the phone number they provided, if you have not already done so. (If they provided one -- I require that all guests provide both verified email and verified phone number). If you don't actually need anything from the guest right now then I would give it some time and wait, and later on ask guest about what time they will be arriving, and questions related to scheduling.
It's not good for hosts to cancel guests' reservations, so I would urge you do not do that unless you have some concrete reason for doing so. And if you did still feel concerned and wanted to cancel, I would suggest calling AIrbnb customer service to talk about it, before doing so.