Does that even count as light for that purpose? Like, I’ve got it on her, and next to her people still got the curse and still got disadvantage from darkness.

Like, is it a bug, or is the light aura just the anti-undead effect and not actually light?

Unless you’re talking about the playtest, DnD you double all the damage dice, not just the base weapon dice. Sneak attack, smites, anything that’s not locked away behind a separate saving throw (like poisons) or just a flat damage boost (like +5 to STR) all gets doubled.

PF2e is great though, would love if one of my games switched over some time.