No, it doesn't sound at all like DM fiat... it sounds like some really poorly planned tactics. Did you go over the fact that Drow are generally really nasty people and that if the PCs were captured they'd likely be tortured in vile, cruel, and perverse ways? Because if you didn't you don't have to do any of that, but from the sounds of things you did. In which, case that's totally fine, let the Drow get things cooking, and let the Paladin player know all about what's going on, and if there's anything she can do. Allow her to act. Start her torture off with run of the mill abuse. That's pretty mild stuff. Basically, what I'm getting to here, is that before anything starts to get X-rated, or close to her gross out level, you can have something happen that gets her off the hook. Maybe the torturers are called off to combat the other PCs, maybe a pack of Delvers are at it again, ruining some of the Drow tunnels, maybe the other PCs actually come to rescue her at this point. The possibilities are endless, and the best part is, you get to keep your Drow seeming disgusting, and vile, and horrific creatures, while you never have to actually go through with any of that terrible gross stuff.