It is pretty well documented that Sabine is a succubus. That certain in-comic characters are not aware of this fact does not make it any less clear to the reader.
Sabine's will save would be +7 from her succubus racial levels, +2 (probably) from her rogue levels, and -4 from Holy Word, for a total of +5. Against a DC of... what, 20 at the bare minimum? (10 base, +7 spell level, +3 Wisdom (since we can't for certain peg Durkon's Wisdom at higher than 17)) So, Sabine would need to roll a 15 or higher to save. So... she has a 30% chance of saving, assuming both she and Durkon have no magic items enhancing things. It wouldn't be unbelievable if she made it, but I'd be pretty hard pressed to call those "good odds"Reinforces? Those are her save bonuses after counting in the Holy Word penalty. She has good odds to ignore the banishment portion of the spell.