Why does betrayal happen between friends?

I have a friend for 7 years. We were close. Her uncle threw her out of the house and she had no other family. I gave her shelter and food, paid for her bills while she was depressed, and when she got better, I gave her a job at my office temporarily even during a rough time financially. I never charged her rent, food, bought her new clothes and paid her a good wage much to my fiance disagreement about hiring her. A year later, I was going through a rough time with my fiance. We had arguments often at home. I crashed physically and emotionally for 3 months and couldn't work. Then when I came back to work, she started to resent me. I was told that she wanted to have a share of a project my fiance got going at work. My fiance and I got married. She told my mother that I force him to marry me for the money (he is totally in debt). She didn't go to my wedding, moved out when I wasn't home and stole the files at my office. We had never argued. I am confused? What happened

She was never your friend. You should have asked her uncle the reason why he threw her out. Take her to court for stolen property. I wish I had a friend like you. I would treasure you for ever. God Bless!

Well, because stuff that happens between enemies is just war.

Sounds to me like she is jealous of you. Not that that's right, but that's a guess as to why she's behaving that way.

She had warning signs to begain with.

Thw orld is changing I have ofte heard about stories like this ever since i was a kid.
I don't know why these things happen.
but you and your friend were friends for 7 years so i don't really know why she would do this to you.
Talk to her about it. i can't say anything cause i don't know the truth. tell her about how her actions are playing on yuo and ask her why she has suddenly tuirned against you.
Sometimes it can be painfull but it's better knowing the truth than misunderstanding one another.

Because human being are selfish.

sounds like you made friends with a backstabbing *****.

Basically, I think she is jealous of you despite the fact you have know each other for long time. You thought that as a friend for such a long time this sort of thing doesn't to you.
Well I believe as long as there is a conflict of interest between 2 person or more, people will always fend for themselves first rather than their friends. So just take this as a lesson learn and be more careful next time