
It is very hard to get rid of the urine smell from dogs and the fact she goes back to the same spot indicates she can still smell it, I use biological washing liquid to clean up accidents, I was told to also use rubbing alcohol as that dissolves the fats in the urine that hold the smell but as I wasn't sure if it would damage carpets I never did.
You may have to go back to basics of house training and not leave her unsupervised where she can make a mess. Have you checked with the vet that she doesn't have an UTI or something wrong with her female bits? Has she had her first season?
It is also worth remembering some bitches will mark their territory.