"(P.S. I know she only dies from being hit by me, I just though the Fus Roh Dah would count as the killing blow, not the fall) "
You are incorrect in saying she can only die by being hit from you. I have no idea why so many people think this but it is not true. She CAN die from a bandit if he is strong enough which most are not.
Lydia died for me when i attacked the Northwatch Keep, she was knocked to the ground 3-4 times which i guess is why people assume she cannot die as she can take a few beat downs... but after she got knocked down again she most certainly did die. I was no where near her during the fight and was using sword and shield so know for a fact i never hit her.
I found those guards quite tough even on expert difficulty and it was probably my fault for not giving her better weapons and armour.