Lila doesn’t really need proof that Marinette is Ladybug
Even if Marinette somehow isn’t Ladybug, she’s still the girl who exposed Lila, embarrassed her, resisted her lies, and keeps getting in her way. Lila already hates her. So from Lila’s perspective, going after Marinette is useful either way.
It reminds me of Spider-Man logic. Spider-Man villains don’t need to be 100% sure Peter Parker is Spider-Man before they start targeting him. They only need to be, like, 20% sure. If Peter is always near the center of Spider-Man drama, close to Spider-Man’s allies, constantly disappearing, and somehow connected to every major incident, then he becomes worth pressuring just to see what happens.
That’s what makes Lila’s current behavior feel weird to me. She’s supposed to be a social/manipulation villain, not just Gabriel 2.0. She should be attacking Marinette’s reputation, isolating her, baiting her into contradictions, watching her disappearances, and forcing her into situations where Ladybug and Marinette can’t both conveniently exist.