Diaper rash ☹️

My daughter will be 12 months in April. She got a hold of my sons milk and has started pooping non stop. I’m trying to keep up with it by checking her often so her rash doesn’t get bad, but she’s pooping a lot. Now it’s the weekend and I’m contemplating taking her to the emergency room to see if she has an infection. 😭 Her poop is kinda stringy looking and it’s almost like it has mucous in it. Any ideas, and what’s the best cream for her?