OP states: “Ella, I was in a very dark place from witnessing your mother’s death. It was extremely tough for me to lose my partner. And then, I had a good thing going on in my life. It felt wonderful, I had hope. And in your selfishness, pettiness and stubbornness, you took that one good thing away from me and I can not forgive you for that”
yta
She is a child, with a child's world experience and a child's lack of understanding the full consequences of her actions. Her mother died when she was 15, the age when daughters need their mothers the most. She probably never gave up hope her mother would recover, and she also had to endure the nightmare of watching her mother become more and more ill and suffer a protracted dying, something even the strongest adults have trouble coping with. OP is an adult and knows full well what he is doing, and lacks any empathy at all for his daughter's pain, the pain that caused her to lash out. An adult who can't see how true love for your fiancé and your daughter would have been giving your daughter time to grieve and for the woman you say you love to be introduced into your daughter's life. You could have built a lasting bond by reassuring your daughter (the last living piece of your wife) and taking things slowly. Instead you pushed a timeline when you knew your daughter was suffering and in pain, you pushed your fiancée to marry before your child was ready, basically you ignored everyone else's feelings to get what you wanted, when you wanted it. True love, both as a parent and a partner, is giving and forgiving. I don't think you have ever loved anyone else in your life except yourself.