Insofar as the mind subsumes the personality, these girls do not share a mind.
Once a society agrees that killing is an acceptable answer to human suffering, there are few logical off-ramps.
Rejection of materialism, on one hand, and understanding and appreciating science on the other — these are not in contradiction, but in harmony!
This was a real-life experience for one family at the Royal Tyrrell Museum of Palaeontology in Drumheller, Alberta.
One just needs the terminal diagnosis — sometimes mistaken — to qualify for the lethal pills.