Sounds like a yeast infection to me (thrush). My daughter used to get that often, and we changed her every 1 1/2hrs...on the dot. Whether she was wet or not. Have you tried Balmex? Or Johnsons 3-1 cream? Balmex worked like a charm for my daughter, but not my son. Johnsons works for him. If you are able to get to a walk in, take her there and ask for nystatin. That is an anitfungal and will help heal her faster and better.
KY Jelly is not for diaper rash. It will not help, nor harm it more. Hydrocortizone will only infect it more. You need an antifungal for this. Neosporin is not good for the diaper area because there is a chance it could get inside her vagina. It clearly states that it is for outside wounds, and if she pees while it is on her, it can pool and get inside of her.
I would recommend buying A&D ointment (not the cream) or even vaseline, when it heals. Be sure to put it on her at every diaper change to avoid a rash. When she does have a rash, Balmex. I found that Desitin burns. My daughter, at the age of 2 (right before she was potty trained), came down with a rash, and i bought some of that. I put it on her and all she could say was "ouch mommy! That hurts! Ouch ouch owwww" I figured it was the cream because she was laying on my bed, bottom up, and the only thing touching her rash was the cream. We dont use that in my house at all. If you can, after her thrush has healed, keep the nystatin in a safe place so you can have it available for when she gets it again (which she probably will) and you cant get to a dr soon.
Good luck and i hope she feels better :(
Hope i helped!