Even if you enjoyed it and would do it again, that doesn't necessarily mean it wasn't abuse. An underage student might enjoy sleeping with a teacher, or even seek to make it happen, but it would still be abuse if the teacher engaged in sexual behaviour with that student.

I think it would boil down to her age in relation to yours, how it began, how it was pursued, and whether or not she had any authority over you (like being a babysitter). I don't doubt the fact that she was abused by someone else played a big role in leading to what went on between you two, but it's tough to say in what capacity.