My (48M) daughter (19F) tried to hurt herself after we found out she’s not biologically mine. How do I help her understand that I’m still her father, and that her existence is the best thing in my life?

My little girl thinks that her existence is evil. We found out recently that her mother, my wife of 23 years, cheated on me when the man claiming to be her biological father showed up on our doorstep demanding to see her and claiming he didn't know she existed. It's been quite possibly the worst few weeks of my life, but she took it so much worse than I did. She calls herself a bastard. She won't talk to her siblings or her mother, and only apologizes to me. I don't give a fuck if she's half t-rex, I love her with every bone in my body, and she tried to take her life last night. My wife found her. She's going to be okay but this can't happen again. I can't talk to anyone about this, I don't want my family to know. I don't know how to be what she needs. Please help.

TL;DR: My daughter isn't mine. She tried to hurt herself. How do I help her?