When Phoebe shows up to save Billie from Burke, Billie was initially shown to be on the ground on her right side. In the next scene, she is on her left side.
When Piper freezes the hospital waiting room, a bald black man is to the right of the screen. For several seconds his jaw seems to be moving around as if chewing, an odd glitch in the editing used to "freeze" the background image.
Keeping the Angel of Death away from Leo would not have saved him from dying, as it has been established repeatedly that the Angel of Death does not kill anyone; he merely ferries the souls of those who die to where they're meant to go.
The sisters and the Angel of Death seem to be the only ones aware of the effects of Piper's spell that makes all men look like Leo.