W.T.
How about a cloth diaper at night with a wool cover? These will breathe so well and aid in the rash issue.
Or, if you don't want to do that, there are "healthier" disposables on the market. Check out seventh generation or some other diaper brands at Whole Foods or Henrys if you have them....they have diapers that are bleach free.
Can you change her while she sleeps when you or your husband go to bed?
How about slathering her waistband area with aloe or calendula or almond oil/coconut oil? Anything to keep the pee off of her.
We cloth diaper, but the few times we've used disposables on our guys, they have gotten those red pee rashes that go away after they are aired out bit.