My son has super sensitivity on his bum from time to time. When this happens, I sit him on the toilet and pour warm water over him and wipe gently with a wipe. I only use hypoallergenic, all-natural wipes.
For a time, my husband was using A & D ointment or Balmex, but I took a sniff of it and detected a slight mentholated aroma. No more of that. If I can smell it, then it may be burning very sensitive skin. When there is a bad rash, I often use Neosporin to take the burn out.
Also, do you powder her? Sometimes powder can clump up and irritate delicate girl parts. When I have to powder either of my daughters, I make sure it does not get near the vagina. Also, you may want to switch out diaper brands. Good luck to you.