Itchy and burning sensation on her vagina two days after unprotected sex. What could this be? No discharge. HIV? Herpes?

Itching/burning. Unprotected intercourse with ejaculation will alter the pH in your vagina. This allows for a variety of organisms, normally in tolerable amounts to overgrow. In addition, unprotected intercourse exposes you to a wide variety of sexually transmitted disease including herpes, HIV, HPV, chlamydia, gonorrhea, trich, syphilis. Yeast and BV are also possibilities. Be smart, protect yourself, use condoms.