Narratively I guess this just demonstrates that you can't save people from making stupid decisions based on limited experience except teaching them by example.
@DragonParadox I'm going to safely assume that she won't flatly say no just in case her Mom is like "uh he offered us what? Well I'm pissed but I also don't think Robert will win, so take the deal", but based on limited experience with interactions with them, can I safely assume her mom is probably hoping Robert and Tywin have some kind of hail mary planned? Or are they literally inconsolable in grief?
I mean did she love her brother as much as Oberyn loves Elia?
Maybe we should just offer to resurrect the dude. We could even track down the soul and say "hey sorry you bet on the wrong horse, want a mulligan?" if he doesn't accept, though that is going so far past bending over backwards that the only thing I can call this social encounter is literally impossible for anyone short of a fucking demigod to pull off.
I get it though, sometimes life is just that complicated and people are basically lemmings who want to die in dragonfire. It's very ASOIAF. Much grimdark.