The thing is, with herbs and dogs....some herbs which are fine for humans to take can be toxic for dogs. So the best plan if you want to go down that route is seek advice (and after all the checks etc have been done with your regular vet -which Ghilly mentioned)....get a consultation with a Herbal Vet or even a Homeopathic Vet.
I'll just mention one thing which may be of some help while you sort out what might be causing this.
DOGGY DIAPERS!
They are wonderful....they will save your carpets, bedding, etc. Don't keep them on her all of the time, but maybe in the evening when she comes in to lay on her bed, or during the night. Disposable ones are available, or you can get pants with an inner liner which are washable, and then disposable pads to go inside. They are not terrifically expensive.
While female incontinence is not uncommon after spaying, there are other reasons that it occurs. Have you had her examined by your vet to determine whether or not it is hormonally induced by the spaying? If it's hormonally induced, there are several things that can be used as a treatment, from estrogen to phenolpropanolamine to ephedrine. However, if the incontinence is caused by a structural defect, surgery can correct the problem so that the dog (and the owners) can live normally without having to deal with the incontinence. Then, too, there is also submissive urination which can give the appearance of incontinence if the dog has an especially submissive personality.
How old was she when she first started leaking?
Does she have a submissive personality?
Does she take medication for anything, and if so, what does she take and for what condition?
Does she drink a lot of water?
Has she ever had a serious illness or surgery?
Does she have any issues with her central nervous system?
Unless your vet has already diagnosed the incontinence as being hormonally induced, the answers to them can tell your vet if there is something else going on that could be responsible for it.
If it IS hormonally induced, the three main treatments that spring to mind are estrogen therapy, ephedrine, and phenolpropanolamine. I am not aware, at the moment, of anything herbal that can be used to treat it, however that doesn't mean that it doesn't exist as I have not studied holistic medicine to any real degree.
Ghilly
Ghilly