She's Anything But an Angel
You have got to cut yourself loose from this woman. "Angel" is anything but -- she sounds manipulative, insensitive, and selfish, and you have been very accommodating.
Lying, Not Arguing, Hurts Your Relationship
It isn't the argument or the confronting her that could end your relationship, it's her LYING!! All the stuff about "protecting your feelings" is such CRAP. I commend you for initially ignoring/disbelieving the rumors from unreliable sources about her lying, but then you got to experience it yourself (you caught her in a few minor lies).
You Crossed the Line
Whether her problem is clinically pathological or not, her behavior does not belong in a trusting relationship. You kind of crossed the line yourself by going into her personal communications, but I have two things to say about this:
- First, I understand how you felt, and perhaps you saw this as a reasonable way to check as opposed to more confrontation.
- Second and more important, however, she just let it go (albeit after an argument and apologies between you both) -- and then continued to violate your trust by not accepting your promise to not do it again (and leaving her passwords as they were) AND by talking to the guy, something she promised you she wouldn't do.
They Deserve Each Other
Frankly, I'm disgusted. These two deserve each other, and you should let them get together and get the hell out of the picture. Being trusting is not a terrible trait, but it can certainly put you in uncomfortable situations with people who'll take advantage of your trust.
Lemme at Her
Find a woman who'll appreciate your willingness to trust and not abuse it. And if I run into Angel in San Diego, I'll be sure to give her a piece of my mind :-)