Help: Is this wrong, who is in the wrong and how to apologize?

Help. If no one wants to read all this well that is just fine because sometimes I don't feel like reading long questions on here either. I will understand. LOL Anyway Thanks and I appreciate anyone that does read this all and answers this question. I'm replacing the real names with fake names. There is a women (Donna) I know that I knew my whole life that I feel like she never liked me at all. Donna stole from me and my parents and she threatened me before and has hit me before like a bully when we were young and in high school. I don't know why casue I use to do everything for her. I use to buy her stuff and let her spend the night at my house and sleep in my bed. Maybe I have done something that hurt her that I didn't realize I did, I don't know, I'm not sure why she treats me this way all the time. I always try to be her friend and sometimes she acts like she wants to be my friend too but then she always does something mean afterwards like make me look stupid and roll her eyes at me. One day on FB, I was trying to help our other friend (Nicole) was asking for advice from people on wheather she should take her cheating husband back or not. So I told her if he truly was sorry and was going to change and go to counseling for sure then yes she should take him back. I believe in God and forgiveness and apologizing so this other girl (Mya) got in the conversation and was disagreeing with me saying she shouldn't forgive him so I was like okay that's fine that is your opinion. Then all of the sudden out of the blue the women (Donna) that always does things to hurt me starting judging me out of nowhere saying she didn't want me in the conversation (which was open to anyone) and was mad I was helping our friend Nicole out or something, (who is really nice and a sweet women never did anything to hurt me) I don't know I'm so confused, Well anyway (Donna) out of the blue started judging me saying I shouldn't be saying anything, giving my two cents in because I set a bad examples for my niece because of some things I have done in the past. Now I know I am not perfect but I didn't judge anyone I was just telling Nicole that yes she should forgive her husband because no one is perfect and God wants us all to look out for each other and forgive each other when we do wrong. I blew up at Donna and started yelling at her and saying I'm sick of alll this stuff you keep doing to me and I can't take it anymore, All you do is steal from me and judge about something that you do the same thing as I do. Donna has set bad examples for her nieces and nephews also and the same thing I have done. She started laughing saying so what you stupid B**ch I don't care about your pity party yadayadayada... I wanted to know if I should apologize to her for blowing up like that and forgive her. Our mutual friend Michelle is having a surprise B-day party I want to go but I feel like I can't go because this women Donna will be there and she threatened me that the next time she saw me she would take care of me as in "beat me up". I can't talk to my friend Michelle's sister who is throwing the B-day party cause she would never understand and probably not care. What should I do? Donna fills peoples heads up with lies about me like she will probably tell our friend Michelle that I am a rotten friend cause I didn't show up to the party. Help should I apologize to Donna or no because I didn't really do anything wrong? I don't know what would be the right thing to do. I ust want to live in peace and say sorry to her but did I do anything wrong and should I apologize? I konda feel bad about what I idi sometimes but then I feel like I didn't really do anything mean to Donna and that Donna was the one doing mean to hurt me.