I would be very upset if my child's ped didn't offer any more that this.
Use Dreft or Tide Free to wash her clothes. If she has any bubble bath stuff, get rid of it. I would give her cranberry juice without sugar just in case she has irritation in her urethra that hasn't shown up in the urinalysis. If none of this helps, I would ask for her to be checked again for a UTI.
Make sure her panties all have cotton crotches. She shouldn't be wearing tight jeans or pants.
Vagisil pH Balance wash is good for cleaning. Tell her to not to use a washcloth on her vulva. Just apply it to the front and back with her hand and then rinse. This product is SO much better to use down there than soap. Soap makes me burn, and the Vagisil has been wonderful for me, so I can heartily recommend it.
I don't know the answer about using Desitin, but I don't see how it can hurt. My son didn't always get his rear end clean and sometimes he'd get red and it hurt. I gave him Desitin to use and he always got a reminder about proper cleaning making it so he wouldn't hurt in the first place, lol.
However, in your daughter's case, it could be that she is wiping too hard after she pees. Tell her to blot instead of wipe. Her skin needs to heal, so maybe the Desitin would help with that. But it won't stay healed if she doesn't do what she needs to do to prevent it in the first place.
Best of luck here...