Certain foods will change the smell of urine, just like in humans. Healthy urine is pale straw colored ( although foods can change the color too)and has a "nutty smell" which is not unpleasant unless its old and exposed to air when it gets a strong ammonia smell as it breaks down the amine.
A "fishy" smell can occur when amines ( protein parts that are in urine)are broken down......this could be from old stale urine smell on the fur but since it persists after a bath she may have a UTI ( urinary tract infection) where the organism causing the infection break down the urine. Most UTI's are easy to diagnose and treat. If she is licking her vulva or fidgety or makes sudden movements when voiding she may be in pain too. I would definitely have her examined by a vet and he/she will do a urinalysis and get her on antibiotics to clear it up.
In the mean time try to encourage her to drink, drink, drink !
