Feeling like I can't empty my bladder is always a first and sure sign for me of a UTI.
If everything comes back negative, you will have to try to get your daughter in the habit of just sitting still and relaxing on the commode and letting it all out. Little kids get busy wanting to do other things. Heck...I'm guilty of that, myself. I find that when I'm super busy at work, I will race to hurry up and pee because I have so much to do. That's not good.
Sitting on the toilet backwards might sound crazy, but let me tell you, the first time I got shingles, I could not pee so save myself. The only way I could even get a dribble was backwards on the toilet. Don't ask me why, but it's worth a try. My not being able to pee became such a problem that I had to be catheterized. Not fun, but I felt such relief after filling up two catheter bags. Obviously, I had an extenuating health condition and I just could NOT pee for myself.
At home, make sure your daughter sits for at least 5 minutes. Clear the back of the toilet off so she can sit backwards and rest her head on her arm and just relax. You can also try running some water in the faucet so she hears the sound of the trickling. Let her take a nice, long, very warm shower before bed and tell her it's okay to pee in the shower. It may sound gross, but I pee in the shower often. I can relax and just let it out. You can spray the shower down with a diluted bleach solution and rinse afterwards. No big deal. It's better than getting a UTI that could progress into a kidney infection. That's no fun, trust me.
Hopefully you can just find some easy ways for her to completely empty her bladder and get into the habit of doing it now before other problems have a chance to occur.
Best wishes.