If you are taking her out every two hours, maybe start going every three hours, and lengthening that time. See what she does. My two don't really signal me either but they pretty much know their schedule. I live in an apartment so have to go out with them. They can got 8-10 hours just fine while I am at work.
If she has an accident, it's just an accident. They happen, even to the most well-trained pups.