The problem is lack of control in her life. Everyone has made the desicions for her and not always with her best interest at heart (not an attack just an observation from what you wrote)
My father controlled my life and I now suffer with anxiety and depression (well I'm heaps better and having 3 miscarriages certianly didn't help!)
This may not help but perhaps getting a part time job some where will help her gain control and self confidence in her life. The only thing she can control is who she see's and who she doesn't. It's almost like anorexia nervosa only with ppl.
I understand your desire for happiness but make sure this time your marrying for the right reasons and that he's right for you. (Read Planning a wedding............Stop and read this first!)
I think also it may help if you didn't live with your fiance to give her sense safety and security. Provide a safe place from the world. It is a huge ask but your daughter is in serious trouble and you need to put your life on hold and help her. Her life is just starting and already she is crippled.
Professional intervention is a must and if shes not getting the help she needs from the doctor she has now it may be time to find an expert in the field, who can provide the help she needs. I don't want to alarm you but what you have described is errieerly simialar to my own youth in the area of control or lack of to be precise. I attempted sucided a number of times and still bear the scars of one attempt.
As you said in your pursuit of happiness, you've neglected your daughters needs, it's not too late, it's just gonna be harder. I would also talk to her father and let him know that she's in trouble and needs help from him. This has to be a family effort and communication is the key. You can't get into the blame game with her father but calmly explain the situation and have him come to the doctors appointments. Remember she's targeting him because she can control it and she can hurt him. She can't hurt you anymore because you've shut it down. This is a war and every battle you fight with her will predict the outcome. The more battles you can win, the closer you are to saving her. Don't take from her rather find ways to communicate and give her back control. You don't have to put your life hold permantly, just enough to get her on her feet and functioning with lifes difficulties.
We all make mistakes and they sure as hell didn't hand out a manuel for raising children! But this is a fight for her life, make no mistake about that. Please watch out for any signs of sucide or cutting or any other signs depression and sucide. I'm pretty sure someone wrote something about both those topics here on Minti, check out www.beyondblue.com an australian site for depression, also check out www.drphil.com he also has some great information about childhood depression and has links on his site to other ppl who can help.
Most importantly seek medical intervention immediately.
Raven