She's a prey animal. When she does sleep, it'susually not for very long, and as soon as she sees or hears you, she'llprobably keep one eye open, just in case. Not that she fears you, it'sjust a survival instinct. All but the most laidback of bunnies will bea little nervous about going into a deep sleep with activity aroundthem.
As an interesting sidenote, I noticed that my rabbits will only go intoa really deep sleep when people are around, if the other rabbit isawake and nearby, keeping watch.
~M