Welcome, and thank you for sharing some of your story, I know how much courage that can take.
I agree with WK in that the end of any relationship can result in having to deal with grief. It sounds like you have experienced more than just the loss of your fiance in a short period of time. I'm guessing when your father stood you up it felt like you had lost him all over again, and after a nasty "hate campaign" you've also lost colleagues and friends. So it comes as little surprise that you would be grieving still as unfair as it may be.
This being said you mentioned that you were admitted to hospital some time ago, are you still accessing professional help? Do you think it would be worthwhile to get some grief counselling? Are you still in contact with your nan? If so, are you able to speak with her? Are you working currently? Have you been able to form any new relationships since last year?
I don't want to steer too far away from your story, however I wanted to share with you my experience with grief and loss... My father had numerous affairs from my childhood through to adulthood (I cant remember how many times I lost him to another family), I lost my first boyfriend to suicide, after being sexually assaulted I lost my second boyfriend and the baby that eventuated from this abuse (i also lost my ability to trust and my dignity), I lost my most recent boyfriend of 10 years because he couldn't put me before anyone else in his life, and I lost all of my friends, my job, and my colleagues at the end of last year...The point of sharing is to say that you aren't alone in how you feel. I completely understand that all of this has an affect on hope, trust, stability, and confidence.
The horrible thing about loss and grief is that you cant get around it, under it, or above it...you have to work through it. I take each day at a time. To help with the process I take medication, I see a mental health professional, I attend group therapy sessions, and I make an effort to have a balance in pleasurable activities and "me" time. So far I'm slowly letting go of the people, the trauma, and I'm rediscovering myself. So it's definitely a process, but one that I know you will be able to take in your own time. My biggest piece of advice is don't let it fester, and don't try to go through the process alone.
This has been lengthy, but I hope that you have taken something from it, and I hope you will keep posting and sharing your progress.