Well, actually, a bone marrow transplant is a stem cell transplant; hers came from cord blood. And embryonic stem cells have consistently proven unreliable; they are in the experimental mode; they wouldn’t use them on humans.
Edit: And even if they did, my nephew & niece would never have consented to their use on their daughter. Most stem cell transplants actually come from the person they are used on, but that wasn’t possible with her. They give them some treatment to cause them to multiply rapidly, and extract them, then replace them in the host they took them from.