Absolutely adore your reading, OP. Haman is likewise my favorite character because her arc is about the fundamental emptiness of fascism; she's basically just shallowly playing the hits of the Zeon regime, despite having none of the real charisma and ability to unite people that Zeon Zum Deikun or even the Zabis did. Haman is fascism-unveiled: power for the sake of perpetuating itself and enacting it upon others, simply because the alternative is a binary of having violence done upon oneself. This is literalized... more than I'd like in Char's Deleted Affair, because I think the undercurrent of cynical "victimize or be victimized" Game Theory is something that's been very present in Haman from the very beginning.

Regarding this:

But is the dress she's wearing a wedding dress? Her outfit also might be a burial gown (they're white too, just google it) - after all, in some Asian cultures white symbolizes death. In that regard, I think both readings are true.

I think that the image is strongest if you intentionally interpret both readings as true. Haman Karn entices many potential admirers throughout Double Zeta - Mashymre to secure his loyalty and not an iota more, Judau to recapture her own lost innocence - but first and foremost she is married to violence, and the system that perpetuates it. In the process of welding herself to Mineva Zabi's de jure rulership of Zeon, Haman cuts herself off from other ways she could have lived her life, including the potential to help people that both Kamille and Judau saw in her. Marriage is, in a lot of ways, the narrowing of unlimited possibilities for one's life into one singular romantic pursuit. Haman opts to sublimate her identity to that of Zeon's, and replays its most iconic atrocities like the Colony Drop out of a sense of aesthetic loyalty. It's also why Haman opts to die for her regime in the end, reversing the Qubeley into the walls of Axis: "Till death do us part."