I'm not gonna lie, that wording does look cringy and weird, and while the translation makes it sound more sexual than the original, the original still sounds weird and out of place altogether.
Issue 1: There was a joke about immersion that wasn't carried over in the translation so the "at least part of it" seems weird and pointless.
Issue 2: Izmar is mostly right about "séduisante" being less immediately sexual than "seductive" sounds, though both can be used with objects, ideas, etc., but if you're talking about a person, you're still thinking about at least sensuality if not outright sex appeal. I would never ever consider calling a child that. I may not be French but I'm not buying that excuse.
Issue 3: I'm not going to try and explain this too precisely, but the way they worded "as seductive as she is ancient" in French is jarring and really makes it sound like "but she's not a loli she's centuries old I swear." Like, why would you even say that? Unless she's an Enutrof that somehow manages to be sexy (pic related), but even then the wording is odd. I feel like the translation actually did better in this regard.
Issue 4: "when she's in the mood" can easily bring sex to mind in English, while in French they made it sound more like a wild child who would only answer when you call her if she feels like you deserve her attention. I suppose they could have gone with a straighter "(if she wants to)".
They really shot themselves in the foot with this, and I can't say the translator is the only one to blame, especially with Izmar saying they didn't even know who Mishell was when they translated this.