Girlfriend bleeding a little a day after sex

Patient: Me and my girlfriend had unprotected sex yesterday. I used the withdrawal method and afterward my penis felt a little sore. But a few hours later we did it again. And i used the withdrawal method again. This morning she told me she had blood spotting in her underwear and i got ver nervous. I noticed i had a rash on the shaft of my penis too. Is this a result of friction from the sex? Why would she bleed?