My friend is allergic to latex and if the guy uses a latex condom she itches terrible afterwards and gets a yeast infection. Maybe she has a yeast infection...they can get pretty bad.

There is usually itching involved, some pain, and a discharge with a yeast infection. Look at the site below and share it with your gf to see if those symtoms seem familiar. Yeast infections are easy to treat and don't go away unless treated. Here is a quote from that site as well

A yeast infection is not considered a sexually transmitted disease, although it's more common among younger women (ages 20 to 40), especially after becoming sexually active. It's caused when certain internal or external factors change the normal environment of the vagina and trigger an overgrowth of microscopic fungi called Candida albicans .

http://www.mayoclinic.com/findinfor....cfm?id=DS00255