So I realize that this is post-TPK and the campaign's dead, but did you ever seriously consider brainwash -> agent of ultimate eeeevil? I mean, it seems to me that the perfect revenge (from a Drow's point of view) for the vile cruelty of inflicting her Lawful Goodness on the world would be to trick/torture/brainwash/enchant/whatever her into the Grand High Evil Warlord of Vengeful Plundering and Evil, or something similar. Plus, it cuts down on the early torture (they want to weaken her resolve, not her heart) and quite nicely introduces the potential of a grand crusade (what else would they want her to lead?) that they might go off and stop, or get caught up in...
Also, one thing that every discussion I've seen on torture in D&D seems to ignore is the great potential for psionics and magic in torture. How about the illusion of burning to death? Cast at a proper power level, they'd feel it without it actually being true - so it'd go on, and on, and on, with no physical damage to the victim. Put them on the rack? Why not just stick them in the middle of an illusion about putting them on the wrack? Saves on space, too (they never have to leave their cell). How about implanting memories through magic or psionics? Let them spend a week magically/psionically brainwashing her about how her party was dangling her as bait on the rope, naked and bound, hoping to draw out the Drow who rescued her. How about researching a new spell, "Illusory Fire Ant Swarm"? Or "Burst of Pain"? Or hell - how about researching a modified version of clairaudience/clairvoyance that lets you feel tactile sensations from a distance, lock it onto some other prisoner, and then torture them to death?
Or what about more subtle torture methods? There's been research on the extremely deleterious effects of extended sensory deprevation. And "Extended" in there gives them a perfect chance to escape scott-free, as long as the rest of the party is on the ball.
All this being said, while I'd never go out of my way to aim to torture a player (and I don't agree with the previous poster who suggested that's what the DM was trying to do), I'm a firm believe in "Are you sure you want to do that?" "Sure." "Are you really sure?" "Yup!" "Okay. Then the rock falls on your head, and you die." I'd rather let the PCs die (...or be tortured) through their own choices than save them through GM fiat and make the campaign essentially without threat.