Hello, I read your letter, I am going through the same thing, in fact my daughter (currently 12 years old) is already living with her father for the past two years, at first it absolutely took the wind out of me, particularly because I have an adult son (28) who never gave me this type of trouble. The first year was absolutely hell for me, since all of a sudden I was alone, however, now in the second year I am dealing with me, for a change, and I am actually enjoying it, I am doing things for myself which after many years, I am able to do. Whatever the outcome, whenever she matures, she will return, I would let her go it will do her good to see that the grass is not greener on the other side. Just remember the more you try to hold a wild horse, the more it will try to free itself, if you let it go and it comes back to you, it was yours from the beginning if doesn't there is nothing you can do about it no matter how hard you try. So commit to yourself, forget about that awful ex-partner of yours, life is too short too be saddled with past regrets. This sounds easy, but it has taken me 2 years to come to grips with it.
Take care,
Christine