Could my 3 year old girl have thrush? White discharge...?

Hi there, last week my daughter started crying when she needed to urinate and saying it hurt so I immediately got a urine sample to the doctor, who prescribed her antibiotics and sent her urine to be tested although yesterday I phoned and got told that the urine sample had come back negative, but the doctor told me to complete the course of antibiotics anyway. Today I noticed a small amount of white discharge in her underwear, could this be a yeast infection? I'm scared please help?