Where Was This So-Called Willingness To Trust?
Willingness to trust? Granted, while I do not believe this particular female is deserving of your trust, I do believe that he wasn't able to give it to her in any way, shape or form. Just one question...how did you KNOW she changed her passwords?? Did she tell you, or did you attempt to check her messages again?
Neither of You Are Trustworthy
There are so many red flags that I can't even figure out where to begin. But I will tell you this...why would you even consider this relationship worth preserving? There is such a lack of trust between the two of you that I don't see how you can ever find a way out of it. You can't trust her, because you've caught her in too many lies, she can't trust you because you have invaded her privacy. It sounds like you definitely do not have what it takes to keep this relationship alive.
Not Everything She Said Was a Lie
As for the lies that you've caught her in, there is probably a VERY small glimmer of truth in what she's told you, and she's built the rest of those lies on top of that. She probably did keep information from you initially because she didn't want to create waves...but also because she herself hadn't decided what she wanted. By making references to going to San Diego repeatedly, you can bet that she's looking for a way to see him and still keep you around in case it doesn't work.
Shame On You
As for you, shame on you for invading her privacy. Once you realized that you couldn't trust what she told you, you should have simply told her that you couldn't trust her. Just as you cannot trust her word, your word is not trustworthy either.
You need to recognize when it's time to let go. Confront her? Yes, and no. Don't give her the option to lie to you...don't give yourself the option anymore to abuse her privacy. TELL her you are leaving, tell her why and let that be the end of it. You are both better off with other people.