Spaying is usually a real good idea. However I would tend to doubt it'd solve the spraying problem in this case. Is she *spraying* (marking) or is she *urinating* (basic body function)? I'm not meaning to be picky, it's just that the cause and thus cure of the two thing is often fairly different. What exactly is she doing?
If it is spraying as in marking, the solution most likely lies in reducing stress. You can try Feliway (it is NOT a drug, btw) but it is unreliable, helps sometimes but by no means always.
If it is that she's routinely peeing elsewhere than the litter box, it's worth a good vet workup to look for physical causes of which there can be many, and if that finds nothing then she may require different litterbox arrangements (size, style, location, litter type, etc).
I would not claim that totally 100% of all these problems can realistically be cured, but a real high percentage can if you keep at it. (Maybe you have, I'm not passing judgement since I have no idea -- I'm just sayin'.)
Good luck,
Pat