it could be that your daughter has had this mild grade urinary tract infection for the whole time..since it started.
UTI's can sometimes continue after all the symptoms have ended...there is just enough of the ecoli to create the foul smell, but not enough to give her the other symptoms.
I would get another urine specimen....you may have to put her on a course of antibiotics for awhile to fully get rid of it.
I had a friend who kept getting UTI's all the time, so much that it was like she had it more than she didn't.
Also, you can check into her diet too.