Thanks for writing in.
Foul smelling urine in your child can be due to dehydration
or a metabolic disorder ( since UTI has already been rule out). Try and give your child some more fluids . Also, we would also need to test the urine and the blood for some amino acids so that we can rule out a metabolic disorder.
Since your child is developing well otherwise, in all probability it could be dehydration and giving her plenty of fluids should be the way out.
Hope this helps