Initially I just replied to the logistical parts of the email and left it at that... but a day later I replied again, said I heard her and was sorry... but also asked her to please not send an email like that again.
Good for you. Setting a personal boundary.
We broke up, it's over, I did my share of the emotional labour and don't owe her any more. If she needs to express her hurt now she has friends and family and therapists who can listen.
Yup. You are the ex now.