The question is whether she is squatting and having accidents in the house, or if she is truly incontinent (the urine just leaks out and is not within her control, especially at night or while she is sleeping). Sometimes some spayed female dogs develop a form of urinary incontinence that can be controlled with medication. Some dogs get urinary tract infections that require antibiotics. Some dogs have bladder stones that cause similar signs and x-rays are needed to diagnose them. Some dogs develop medical conditions that cause them to drink more water than normal, and then subsequently have to urinate more often or larger volumes. She will need a check up at the vet to help figure out what is going on. I would bring a fresh urine sample with you if you can catch some while walking her, and be prepared that the vet may want to run some bloodwork as well.
BTW, eliminating all medical causes, dogs don't pee in the house because they are mad, or seeking revenge. They really are not capable of such thoughts and behavior. Often it is stress because their routine has been disrupted in some way.