How long has it been irritated like that? It looks like there's a bump or swelling on the one side? Keep a close eye on her, if it starts getting crusty or wet looking, feels warm to the touch or develops an odor you will have to bump up your vet appt as untreated pouch infections can go systemic quickly. Have you seen her grooming her pouch? I know it's hard to tell by a picture, but I've seen my girls pouch looking a little swollen after a big cleaning session. It went back to normal in a couple hours, though.
You should probably make an e-collar and have a hospital cage ready in the meantime in case she starts selfmutilating.
When you take her in, make sure your vet swabs her pouch and does a culture if it's a bacterial infection to be sure she is prescribed the right antibiotic. Keep us posted! I hope she is on the mend soon.