I thought the whole reason there was any ambiguity over what Sabine is was just a jab at the "golf bag syndrome" criticism sometimes leveled at 3.5. Hence why Haley shot her with Silver and Cold Iron simultaneously to make sure it hit, since she didn't know which one it would take, but then she didn't know which one actually hurt her. Sabine is a Succubus, per the SRD thus it was the Cold Iron arrow that actually hurt her, but it was very unlikely that a rogue like Haley would have the Knowledge skills to know that. (Knowledge: The Planes DC 16 by the RAW to know the common weaknesses of a Succubus, which is not a class skill for Rogues)
It's not like V (or the Monster in the Darkness), where the exact nature of the character it is a main running gag of the strip, with Sabine it was a one-time gag fans have dissected ad nauseum.