Before birth:
Mr. and Mrs. Fereira - girl XYZ
Mrs. Herault - twins A and B
1) At birth, girl XYZ is probably killed at birth, she's "replaced" by twin A, she's called Fanny. At the same time, the Doctors told Mrs. Herault that one of the twin is dead...
2) Mother goes away with twin B...
Sister B was not killed in the accident. The accident was staged by the mother to protect sister B. The mother cut a finger of the sister B and used the body of an already dead girl (remember: the highway employee said that the only thing intact after the accident was a finger the mother was...
My thoughts:
Judith was swapped with one of the twin sisters (sister A).
As they grew older, the remaining twin sister -sister B-(probably living with her real mother) became a "danger" for those who swapped the babies: why two girls, born from supposably "different" couples, would resemble...