Okay, herewego. I told myself I'd try this with a generous outlook.

Dear Mandy,
I am sorry I've been so cruel to you throughout the years. I am even more sorry for the past few months in particular. I have been beyond cruel to you, both mentally and physically. You do not deserve the tortures I have put you through. Although it remains clear that you're not the coolest cat in the crib and that there is plenty of room for improvement, this does not justify my bullying. I'm going to try to be kinder to you, and do things properly. I owe you that much. And really, I only get one of you. So let's make this work.
Sincerely, yourself.

Blaaaaaaaaaaaaaaaah, I'm ready to fall asleep now. Come on eyes, let me do it.