I agree, confine her to a smaller area. I've experienced angry poop from Uni before. I do believe they know exactly what they are doing. I also believe that you don't need to catch them in the act of peeing or pooping to correct them. They know it's theirs, they know the smell. Plus there's no one else there. When we were training Uni, if we were to find a new spot, we'd take her back there, and we wouldn't even have to make her smell it, you can tell by the head and ear position that she was cowering a bit, and scared. A firm no, and bring her to the place where she is supposed to go.
You said you got her as an adult right? Perhaps she is still getting used to her surroundings? Give it some time, no dog will be 100% accident free in a new environment.
BTW, I see you are from DB, I grew up there. My dad still lives there, near the LA fitness on Golden Springs, closer to Rowland Hgts side.
Have you ever been to the sushi place next to the Papa Johns by Ralphs I think at Grand and DB Blvd? That is my favorite sushi place in the world!