No decision would be truly perfect, allowing the most ideal outcome without leaving a single possibility for a potential flaw or loss resulting from it.
Risks were being taken regardless of what decision she would have made related to Cedric and his group.
Even if she later found out that she made the wrong decision, there was always time to change her mind and to correct herself when it was required of her.
Just as she could find another opportunity to kill them if she were to go to such extremes, it was just as possible for her to cut off all contact with them and disappear from their lives.
Her way of dressing and her background story had done their job enough to make it difficult for them to find her later.
It would be just as troublesome for them to be able to recognise her unless she messed up in the future and started showing her true face to them without hiding it.
