@lulu275,
I agree, hate is such a strong word and really, is a waste of energy.
Perhaps she wanted to apologise? 2 years is a long time, maybe things have changed for her, perhaps as a result of what happened she attempted to better herself? More than likely she needed some form of closure, I tend to think if someone emails after that long and after a nasty breakup that could be the reasoning.
I think I would be curious and I agree, if there was nothing in there that mattered to my life, or something perhaps I should have read/heard I just wouldn't answer. If she is just after closure and says sorry? I don't think there is any harm in saying, thanks good luck with your life and even block the address if you want after that.
An act of kindness can go a long way and can also surely make you simply forget what happened and just move on with your life as well without having that previous last thought, rather this one.