I think she wrote the letter...and the site is a 'safe' place to write it.
ILMAG - this comes from your broken heart.
I know you and your dad were closer once. Have you considered giving him a copy of this letter?
With maybe one change, like here: "You continue to unknowingly break my heart every day. I'm happy that you are happy with your fiancee, but it seems like you have changed in so many ways since you have been with her... I can't begin to count. I want my dad back, I want my best friend back. I want YOU back."
This way, you are saying how your dad has changed, and not blaming someone else for it - so it puts the response on him to answer you (and keeps hard feelings from getting in the way )
He may not really know exactly how you feel, and this tells the story, clearly. Think about it, k?
"Remember that children, marriages, and flower gardens reflect the kind of care they get." -- H. Jackson Brown, Jr.