They can go long periods without pooping, so don't hold your breath, lol. I wouldn't worry unless the area right before the tail looks swelled up like a water balloon. Then she could be blocked up. If she has passed urates then I would think she is not backing up. Soaking is the best cure for what is usually a blocked urated possibly from dehydration so it sounds like you are doing the right thing. Pictures are always worth a 1000 words. Post one if you see swelling.