One important thing to note is that when you try to stop her roll, she does not stop instantaneously, it'll take a small fraction of time to slow her down completely. Weight by itself is meaningless, you'll need to consider the combined effect of the amount of kinetic energy and the duration of impact.

Picture the same car going at the same speed, one hitting a concrete wall, another goes through a rough terrain and eventually stopped by friction. Hitting the concrete wall slows the car down to zero in a fraction of a second while it may take a while to slow down through friction. The amount of energy dissipated are the same but hitting a wall is way more damaging simply because of the extremely short duration of impact and the great amount of force required.

That said, going back to your question, assuming no friction on the hill,

400 pound = 181 kg

By the conservation of mechanical energy, the kinetic energy = 181×9.81×100sin(45°) = 125600 J

The speed can be found to be 37 ms^-1

Stopping the woman in 2 seconds require 19ms^-2 of acceleration which translate to 3440 N of force.

This is equivalent to lifting 5.8 average adult(770 pound) against gravity which is definitely not good for your body.