Pretty bad rash

Anyone else’s baby had this diaper rash? it was getting better but I can’t even let pee sit on her for a minute. Her diaper immediately has to be changed or it’ll get worse.. I’ve been putting Vaseline on it bc it’s a skin protectant and healing agent.. when I sit her in the bath she kind of scratches at it 😫 I’m a first time mom so I’m completely sad about this.. idk what to do.. it looks so bad to me. this is the first day looking this way.. she’s 10 months btw

It’s on both sides and on top.. nothing inside.. my mother suggested it looks like a yeast infection for babies but HOW?? I’m so confused