Litter box problems are sometimes the most difficult to deal with, and the longer it continues the more of a habit it becomes.

As for removing stains/odors I use Vet Solutions Carpet Stain & Odor Eliminator. I don't know about ordering from that particular website, the link is just so you can see what it looks like. We sell it at work, but I don't know that all vets carry it, some pet stores might. I've used it when I've been potty training kittens and for kitty vomit stains (heck the stuff even worked on a mustard stain on light colored berber carpet!) I've had a bathroom rug I once washed in fabreeze and it still smelled of cat pee, but once I used the odor eliminator the smell was totally gone.

If she's peeing on the actual wall itself then your problem isn't just confined to the carpet.

Is she the only cat?
Is she spayed?
How old is Ashely?
Do you know if the previous homeowner had cats?


As far as her behavior at home try:

Adding another sandbox with no hoods, or liners. Rule of thumb is one box per cat plus one extra. At least one of those on each level of your home.

Fill second sandbox with plain clay unscented litter.

Scoop both boxes out once a day or more.

Dump out clay litter totally once a week/clumping litter a little less often, and put at least 2" of totally fresh litter in.

When you wash out the litter pan only use plain HOT water, no soaps/cleansers/chemicals.

Ask your vet about Feliway (a pheremone spray), although if you can't get all the odor out, I don't know how much help the Feliway would be.

Seriously look into the walls/baseboards to make sure that urine hasn't penetrated those.

Good luck.