In the best possible world, we have just agreed with each other. Sabine is a succubus and a succubus is always going to have a cold iron weakness instead of an adamantine weakness, but Rich could do something crazy and give Haley the appearance of Sabine not being vulnerable to her cold iron arrows if he really, really wanted to.
What's really interesting to me is how we are both drawn to such wildly different interpretations of the bet. You think ZhonLord is saying something about a part of Sabine's character that can't be changed, I think he is saying something about an upcoming scene in the plot that hasn't been written yet. So you think you deserve the bet early, but I think we have to wait and see if Rich does something crazy.
Yes, we could ask ZhonLord to clarify, but that doesn't really change our personalities, it just forces one of us to admit we didn't understand ZhonLord. Let's assume it's me. I could lay a bet down right now: For one Bedazzler branded rhinestone stud, I think Rich is going to arrange the plot so that Haley shoots cold iron arrows at Sabine and they do no damage. Haley will comment Sabine is no longer weak to cold iron.
Do you still want to collect your stud in advance?
Yes, this is exactly why I didn't like that example. How do you feel about Crystal coming out as a Golem? That's a big wildcard.
Imagining something similar happening to Sabine doesn't make me think, "Is it possible?" It makes me think, "Does Rich have the narrative focus for this?"
That's slippery for me because I'm not great with the 3.5 rules. There could be an obscure feat somewhere that swaps out your weakness, and that would drastically reduce the narrative focus needed to leverage Sabine into an adamantine weakness. There's already an artifact in play that could do almost anything, but there the narrative focus required is shifting away from the expectation Rich has been setting that the artifact's power is intended for some purpose other than powering up Sabine.
Despite all that, Crystal's Golem story makes me think Rich does have enough focus left to do something like this to Sabine, but it would leave little focus left over for other things in the story that I'm quietly hoping for, which is why I bet against it.