Why did my SO go through my messages?

My GF of 13 years knows I'm a member of Chambers and has herself an account. I went and made an alt account to post some things and have some discussions on chambers that I don't want her to find out about. She found my alt account (otherwise this wouldn't be here). Then she proceeded to go through my messages and send the person I was talking to and say that she is me. I know this because the person that she continued to talk to sent a nark and that's how I caught her.<br><br>I'm feeling a bit miffed that not only she found my alt account but then she proceeded to go through my messages and subreddits. I know that she knows and I'm going to have a chat with her about it tonight, but it's just really unsettling to think someone goes through all of my shit.