If you are riding down a road that you don't feel you can slow down safely or use a pull off or pull over a bit to the side to let a car pass you - and by nature it is a 1.5 lane road in which 2 way traffic goes... Then you can't safely go down that hill - because what the hell are you going to do if a car is coming up the hill at you? You guys can tell me all about how the car should give way because there is no way that the cyclist can safely give way, but the reality is that if there's no way that the cyclist can safely give way or slow down, then she shouldn't be there.
And if that's the case that it is not safe to slow down going on that hill, or pull over in a pull off - then really, you shouldn't be lapping that hill. If you live in that neighborhood and you have to go down the hill to get home, then okay that's one thing - but doing that hill repeatedly isn't safe.
Op said that the rider was riding her brakes all the way down and going slowly - if that's the case, it doesn't sound like a situation where pulling over into a pulloff would be hazardous to their health.
I think op presented her concerns and how surprised she was to be irritated at the cyclist very honestly.

