What Causes Itching In Pubic Area?

Hello . me and my girlfriend had unprotected sex four days ago and it was her mid perior of her menstrual cycle. I did not eject semen inside her vagina but i just thought may be some drops left in there . so i got her postinor and she took it in time . today she complained of some kind of itching sensation in lower abdomen more towards her sexual organs . please help me what is going on ?