Oh God, I went through that last Monday.. Roommate was still in bed when I got up (she usually goes to work before I go to school) and she told me she had been sick during the night, and I knew it wasn't food poisoning because we had eaten exactly the same things too (which I had prepared). I ended up leaving the apartment the same day, cause I was worried about catching it. Turns out it was a sv, she was sicker the next day. You should still disinfect the apartment, that's what I plan to do when I'll come back. Bleach works the best for noro and the such, so use that where you can and use lysol on the other surfaces and you should be fine. You're probably in the clear if she was only sick once, though. Friend of mine has a weak stomach too and often gets sick because he ate something too rich or that he wasn't feeling like eating.