The first thing is to take the Blizzard Potion and perhaps Swallow. Remember to use pause if you need to. In the corridor, go past the first set of supports (ignore them) and Ard the second set of supports. The Queen will now be much slowed down. You will have time to get through the corridor and into the main cavern. If you have time, loot the corpse off to the left just past the second set of supports. If you can't, don't worry. Fight your way through the workers but don't try to defeat all of them. Just fight the ones you have to, Igni to clear a path and get to the main room. Across the room, off to the right there will be a blocked exit tunnel. When you get there, turn around and Ard the last support you pass as you arrive at the exit tunnel. The ceiling will not cave in until the Queen gets there. Go back a safe distance so you don't get crushed. After the Queen dies, loot her corpse and the tunnel behind you will open up. Be sure to loot the chest(s) on the way out as well. I was ready to quit The Witcher because I was so frustrated with the Act III boss (The Kikimore Queen), but gave the Blizzard approach a try and succeeded. I was not able to loot the corpse, but so what, I'll try that later. This boss character is harder than Duriel in Diablo II, but you should be able to kill her within a few tries. I tried MANY times but succeeded the first time I tried using the Blizzard potion.Check out YouTube if you want to see different methods of killing the Kikimore Queen.