Theft is a forgivable sin, but betrayal is betrayal whatever the situation.There are reasons to steal, there are never reasons to betray.
I had what I thought was a good friend betray me by saying she was at home, when she was really in the pub, and proceeded to read some deeply personal phone text messages out loud to a pub full of work colleagues.... Consequently this went round the entire building that he and I were 'at it'. She vehemently denied all knowledge, until a third person confirmed that's what she'd been doing. She'd deliberately tried to damage a special friendship I have with a guy whose pants she wants to get into and mislead these people into thinking I was having an affair with him..... she also made up stuff to try to make me hate him, stuff that I knew that he wouldn't do, so I called her bluff with it and told him. She'd be furious if she knew she just made us closer now......! The main thing is, she did it purely for her own benefit and entertainment, to try and destroy what she saw as competition..... people like that are bad news and should be avoided... I can't do that, I work in the same building as both involved parties, so I have to live it down.
If this person is a true friend, they would do anything to stop you being hurt. If this person were a good friend, they would know you were relying on them, and that they could do the same. Outing someone as a bastard in public doesn't work. As with my former friend above here, she needed to be proved publicly as a liar. She's done this herself and is reaping the consequences. If there is a criminal matter involved, go to the police. If it is just personal, try talking to the person and ask why they did it.... what ever you decide, public lambasting isn't the way to go.
Trusting someone who has once betrayed you is the most difficult thing in the world. I've only managed it once, and it took a very long time. The simplest resolution is to 'chalk it up to experience' and move on.
LTS