Yep get a urine test. DD had two UTIs last year (age 2) and I only knew something was up because of the weird smell. Apparently when they're less than 2-3 years old the don't complain of pain so don't wait for that to be a sign.
I believe it's standard to then get a kidney ultrasound after testing positive for a UTI, so if your DD has an infection your doctor should organise that. It's just to make sure her kidneys and bladder are all good.