I guess the question is.. What is your goal in contacting her?
If it were me, I'd consider writing a very short note of what I felt and understood without defending going to college, etc. (And sometimes one additional reason young adults get married is to escape a bad home environment.)
In the end she was a helpless child, alone in a disturbing home. Write from the heart to her. Your realization and understanding of what she went through. Your remorse. And let her decide her next step.
