That does not follow at all. She was only conceived without sin through the application of Christ's sacrifice. She was saved by her Son, just like the rest of humanity; it's just that the salvation was applied retroactively in time. Also, it was not necessary that she be sinless...this is simply a sign that she was the immaculate ark of the new covenant.
"She was only conceived without sin through the application of Christ's sacrifice."
Not sure I follow this at all. Do you mean she was physically conceived by her parents in sinlessness?