Severe diaper rash

My niece has a really severe diaper rash. Her whole area is bright red and bleeds during wipes sometimes.

My MIL is kind of like her second mom (she has my niece at our house with us for the weekend), and she showed me her rash and asked for ideas to help cure. She’s been to the dr 4 times for her diaper rash that’s gone on since may. And it’s bad ☹️ I was shocked when I saw it. Nothing seems to help she said

I’ve never had to deal with diaper rash problems with my daughter, so any ideas or advice will help