After her health bar was completely drained, it disappeared and she just kept tanking hits like nothing happened. I only hit her with the basic projectile attack while using the power amulet.
Regarding jumping: In the classic series, Mega Man's upward velocity wouldn't instantly be reversed if you released the button mid-jump. His jump would immediately peak before he accelerated downwards, said acceleration being faster than that of a full jump but not instantaneous. In Mega Man 1 and 2 he would take a brief moment to decelerate and reach the apex of his jump after you released the button, but those games hadn't yet nailed the proper Mega Man feel.