If they are so self-absorbed as you describe - then what the [insert the expletive] would they care about facing "the world of self-absorbed people who would judge them,... on their outward image"? Sorry, but your statement is self-contradictory, and thus does not hold water. Self-absorbed person does not give a ******* about the others, or the others' opinions and judgments - for then that person would be absorbed not in oneself, but in others. She wants to face her world on her own terms, not as an invalid, but as a person in control - of her own bowels, among other things. Understandable - and may she get her wish.
Self-absorbed as in absorbed with how others view them. Shallow. "Death with dignity" is just offing yourself before having to face a life with which you're not comfortable. I think more than the potential pain is the potential non-support of the self-absorbed peers that don't want to deal with someone who has a terminal illness.