The article didn't tell what the old and new blood types were. If it went from O to another type or A to AB or B to AB, then it would seem that the marrow might be producing both old and new blood. However if it went in the opposite direction, that means that her own marrow was completely supressed by the new liver. Similarly only a change from positive to negative would be really shocking.
She went from O- to O+.
I was at a dinner with one of the Doctors involved the other week. They told me about this in conversation, but I don’t remember all the details. Do remember that one though.