Instead of trying to save Ana and then having Ana saving the day, I would love to see the following alternate story line. After all, we are the heroes, are we not?
It would start with Elminster telling us he wants to go with us because Ana is much to important to lose and he himself must come to her rescue. We would meet him at the CitW entrance (after entering) and we should help him battling demons until he can rescue Ana.
Then we would do battle (with Elminster casting something useful from time to time) until we can free Ana from whatever prison. Of course this would alert Lolth immediately who would give her long and nerfing sermon now and tells us that this is most convenient, her worst enemy, the rests of Mystra and some lesser heroes that would make good casting components for her rituals to become godess of magic. She even taunts us deeper into her web.
We try to protect Elminster and Ana to retain our freedom of Action - we do not want to get overwhelmed by Lolths minions, legs, whatever. After some time this annoys Lolth and she herself steps in to stop this bickering. This is used, with the help of Ana, to spring one of Elminster´s magic traps. He temporarly forces Lolth to manifest and to be vulnerable for attacks. Now a really epic battle evolves. Lolth summons in whatever minions are nearby and the party has all hands full to do to clear the back of Elminster and Ana from thrash while they battle Lolth themselfs.
Of course, Lolth wins the upper Hand and bannishes Elminster back to the FR. With his last gesture, he takes Ana with him and the party is left with a very angry Lolth, that still is vulnerable and has used up much of her power, and whatever thrash still is alive. Now the party has to force lolth to either open a Portal back (by nearly killing her or whatever) or to flee from the web, with a very angry Lolth harrasing them all the way out. Then there is the final battle with the angry but vulnerable godess.
In the end, the party should be able to fight a major victory over Lolth, with forcing her to retreat, a feat that even Elminster could not do. The party returns to Eveningstar, only to be praised by Elminster and Ana for "you did what I could not" and claim the prize.