Dear …
Those things you said to me the other __(day/night)__ were very hurtful. I never would have thought you would do that to me. To be honest with you, it’s actually changed the way I think about you as a person. That is why I am glad to have received your apology letter, which has somewhat softened the blow.
Being __(told you are/called a/accused of/etc.)__ __(briefly describe the most hurtful thing said - i.e. an unfit mother)__ wounds a __(person/mother/etc.)__ more severely than anything else and I don’t know if I will ever fully recover from those words. They really cut to the core. But I do appreciate that you have made an attempt to make it right.
I have to admit that it’s been hard to think of you in a good light these past days __(Name)__, however, I do accept your apology and will try to put all those hurtful words behind me now. Thank you for taking the time to send me an apology.
Sincerely,