I'm sorry you had to go through such a tragic experience. These are some of the most difficult decisions a (potential) parent must face. But I think you made the right choice.

It's easy to imagine that people would always choose life--the living, aware, conscious do--and that to do anything else is to let them down in the most horrible way. But what about the potential for a person?

If we could imagine how a virtual, grown, XX Sierra would respond, I think she would say: "I was only ever potential. I'm sorry--I was too unlucky. Thank you for caring for and loving my siblings and making their potential real. They deserved all your love and all your effort. I would have had trouble understanding, but if I had known the burden I placed upon all of you, I would not have been able to bear it. I could not have given you what my love for you would have told me I must give. Thank you for thinking of me, and thank you for being able to let my potential go."