As a doctor, you should always take the one whose life is most endangered. Treat both and move the more stable one to another hospital.

If all things are equal where it was just one or the other, I'd admit the step mom, as she demonstrated that she was the kinder more descent person, and thus a greater loss to the world.

This circumstances bring to mind the story where there is a mad bull on the loose and it doesn't matter what you say, the answer always close any possibility and corner you towards no escape. It seems to me you are setting similar conditions for us to say what you want to hear (of course I could be wrong). The cold fact is the hospital purpose is to provide help to the one in most critical condition regardless..... That would be my guess

Your Hippocratic Oath would require that you take the one who was more severe

I would imagine the right thing to do would be to let the nurses at triage figure out who needed the help more. But that's not what you're asking, is it?

All other factors being the same, I think the answer is obvious.