this question about Amelie and Gabriel's secret keeps popping up in fan discussions. From what I recall, Amelie—being Gabriel's sister-in-law—doesn't seem to know he's Hawk Moth. The show hints at her being more focused on her own family drama, like her son Felix's antics. She’s got this icy, aristocratic vibe that makes her seem aloof from Gabriel’s supervillain life.
That said, there’s this one episode where she visits Paris, and you can’t help but wonder if she’s picking up on something. The way she side-eyes Gabriel sometimes feels suspicious, but the show never confirms it. Maybe it’s just her general distrust of people. I’d love if future seasons explored this more—imagine the chaos if she found out and blackmailed him! For now, though, it’s all speculation.