Yep, my guess to would be a yeast infection or a bacterial infection. Both which are common, but do need to be treated by a doctor. Once that is done you can resume a normal sexual relationship.
Red and itchy? She needs to see a medical professional and get a proper diagnosis. It could be a yeast infection, based on what you're describing, but if she's never had one before, then she will need to see a doctor before moving forward with any kind of treatment. As for the anti-itch cream, don't treat the symptoms - treat the cause. The cream is only a band-aid fix.
In the meantime, use condoms during sex. If it is a yeast infection, it can be passed to you (under foreskin and around head of penis). This would become a real pain if she got treated, then kept getting the infection from you over and over. Good luck!