And that's why we have statutory rape laws. It doesn't matter if she gave her "consent" to the sexual activity. The law (rightfully) presumes that she is incapable of grasping the circumstances and consequences. The moment this 18 year old began getting physical with her, he became a rapist in the eyes of the law.
Pennsylvania Consolidated Statutes
CRIMES AND OFFENSES (TITLE 18)
ARTICLE B. OFFENSES INVOLVING DANGER TO THE PERSON.
CHAPTER 31 - SEXUAL OFFENSES
§ 3122. Statutory rape (Repealed).
§ 3122.1. Statutory sexual assault.
Except as provided in section 3121 (relating to rape), a person commits a felony of the second degree when that person engages in sexual intercourse with a complainant under the age of 16 years and that person is four or more years older than the complainant and the complainant and the person are not married to each other.