Memory is a trickster. As you mentioned what you remember is hazy. Yet you are judging your past from the perspective on what you have learned years latter. Your 12-year-old self didn’t know what you know now so judging her by what you know now is unskillful. We all feel regret for some past action or other, but all the regret in the world isn’t going to change the past. The best we can do is that when we learn better we do better.

Its clear you have learned something about yourself from the experience and realise that such actions are not who you are or want to be… so I don’t see the point on remaining fixated on the memory.