There are various options.
Grüber, Stanford, Savvy, the whole internet – for she’s verified what they’d said about the Lefatigué family on her phone when back in the room – are part of some sort of elaborate put-up job; the family line is not in fact extinguished, and the lady she’d met is indeed whom she’d claimed to be. But this is neither likely nor feasible: think of all the people that would have to be in on it, all the technical legwork – and there is still the question of why they’d go to all that trouble. So, she thinks she can cross that one off the list.