That happened to Miko when he was around that age too...I had them do a urinalysis and a urine culture, but they said he didn't really have a UTI. They sent him home with antibiotics, but I wasn't satisfied with that. Well, it turns out that he had crystals/stones
Instead of taking in a sample of urine, you might take her in first thing in the morning and let them get an uncontaminated sample themselves. Tell them to check for crystals and stones, and if she has them, have them analyzed. They might want to do an x-ray or ultrasound to check for stones. Certain kinds of stones do not show up on x-rays, only on ultrasounds.
I hope your baby girl starts feeling better soon!! She's such a cutie pie!