Where do I find the key card in 5-1 to let ashley out?

Beat a special zombie.

You have to beat/kill the regenerator's sister, a.k.a. The Iron Maiden. So how to get there? Go to the only door possible and through that door you will encounter 6-7 ganados that is much not of a challenge, then get down there by the stairs there should be a door. Now, once you get through that door, there will be 2 gates, the metal door and an ordinary door. The ordinary door has a typewriter, so go through the metal door, there should be doors again, once you go through a certain door in that area there will be a monitor showing the door you just came by, a regenerator that is shaking like it's been stuck at antartica for 5 years with spikes, there is a shiny thing with him, kill him and there you have it. The Iron Maidens are like normal regenerators except that they have plagas on their back which means after shooting all the plagas in front, shoot it in his knee(make sure you have enough distance from him coz he will bite you like a woman) then shoot the plaga in his back.