That is funny. Which part of her are you worried about feeling pain? Her feet? Her head/brain will be laying on the stump. Will there be some cognizant thoughts running thru her head? Maybe yes, maybe no. The amount of trauma will short circuit her nervous system and she will not comprehend any of it..... Will she feel pain after her head is gone.
The first definiton of humane is kindness and mercy. You are doing that.