Honestly, the misunderstanding is intentional. After all if I just said "btw this is an illusion" then everyone and their dogs will ignore them. By keeping it vague but also questionably possible then people will react to them as if they're real. Especially types like Helena who "shouldn't" be hurt, yet still are, so they'll either need to decide if Fran is just faking it (she is) or if she's actually capable of hurting them (she is).

After all it's a pretty shonen tactic to have the big talker have to try to maintain the illusion that he's as strong as he says he is, and somehow or another through trickery, cunning, and sometimes even real strength, he manages to prove his worth. That's what Fran is here to do, in this character development battle arc.

Tl:dr in order to trick your characters, I need to be able to trick you.