Conclusion
Since I took a more optimistic attitude toward this situation than did Rita, I was well able to allay her anxieties, and to calm her down. To tell her boyfriend the truth seemed to be a needlessly cruel thing to do. There was a solution if this was a much older couple and if the man involved with Rita were quite mature and sophisticated.
But, obviously, considering the age of the people involved, such forthrightness would merely cause great pain and confusion.
My advice to Rita consisted of a simple thing:
First, explain to her boyfriend that she had been involved seriously with one other boy before she met him, and that she had intercourse with him once. But their relationship was definitely finished, and she regrets her action.
Second, do everything possible to build a healthy, satisfying relationship with her boyfriend and future husband, and;
Finally, to appreciate that she did the only sane thing she could have done, even if she did it a bit late-namely, have nothing whatever to do with Phil, the older man who violated her, and never to see him or contact him again.