it could be worth a trip to a GOOD vet sometimes it is a bladder problem that can be fixed, if not it is very hard to break them of the habit, you could refine her to the laundry with a litter box and teach her to use it, but it would take perseverence. sometimes they just spray because they are not happy, my sugestion would be bring her inside and see what happens, you can always use a spay bottle with water and a little bit of vinigar to squirt her if she does it in the wronge place, also clean any messes with vinigar as they don't like the smell.
good luck with it,