Dear Mrs. Weasley,
I know, I know. You want me to call you Molly. I can't. It's just too weird. But forget that. Today is your birthday. And I know Gin, the kids, and I already gave you your birthday gifts, but I had one more that I wanted to give you.
I met you when I was only 11 and, when you found out who I was, you simply took me under your wing. Over the years you have treated me like one of your own. You've given me hugs, lectures, punishments, and chores. You looked out for me, made sure I was eating, and gave me a home. We've had long talks about becoming a parent, about raising children, and about handling Ginny when she gets "unreasonable." There hasn't been a moment since I was 11 years old where I couldn't rely on you for help or for words of wisdom.
So on this birthday I want to give you a gift that you have deserved since I met you, a gift that comes straight from my heart. You're no longer Mrs. Weasley to me. Never Molly. Now and forever, you are my mum. You have been for a long time. I was never sure if it was okay to call you that since you had your own children and I already had a mum, but it feels so right to call you that. You have loved me unconditionally and I am what I am because of you.
Thank you, mum. Happy birthday, mum. I love you, mum.