I agree, she just needs you to love her and affirm that love. What was done with the bf last summer is done and over now, so even with regret there's no undoing what's done.
Now, she needs to move on more carefully. Since it's clear she is loved and supported at home, I think it's far more likely she will have learned from this experience and make safer choices in the future. I'm so glad you stressed the importance of her taking good care of herself and protecting herself!! Had you responded in anger as some parents do, how could that message have gotten through? You also made it clear that she can come to you with the big things, and that is very important.
Never linger too long with the ignorant,
throw stones at their talk.
Walk only with the lovers,
the mirror of the soul gets rusty when
dipped in muddy water.