It was a driveway that is more like an alley than anything else. I had slowed down so it wasn't a high speed thing, just enough that I landed on my side the wrong way. I think we were both partially at fault, but she really shouldn't have been riding the wrong way down a sidewalk on a one way street.
Kaz, it's exactly as you said. I focused on the direction from which traffic is coming, even after glancing in the other directions as well as I could but the edge of the building was in the way of having a clear view.
Oh well, **** happens. Guess I'll be more careful in those situations.