<human>: Background info: I suspect my sister cheated on him, something I frowned upon and often asked about, which she denied always, but she was going out "around town" with a boy behind her boyfriend's back, a boy she used to hook up with in high school. 

Last night they broke up, but she only told me this morning. I asked for details and she said she didn't want to talk about it. Later, I asked her "Well can you at least tell me who broke up with whom?" and she snapped "I don't want to talk about it with you!". I got a weird feeling and asked: "Is it because you think I'd judge you or something?" to which she replied that I don't do anything but judge her, and that I always give her lectures, and that it's pathetic that I, of all people, think I should get the right to tell her what's right and wrong. That stung, since I always try to be on her side, but I do sometimes alert her when I think she's wrong about something. Also, why would she say "You, of all people." I never even had a boyfriend. She was referring to the fact that when I was 18 I kissed a married guy, something that I really regret, but honestly, it was just a peck on the lips.

I feel really sad because she won't trust me enough to let me be close to her. I'm her sister for Christ's Sake! I want to be there for her but I got so angry by what she said that I haven't spoken to her since. 

How the hell do I make my own sister trust me?

Can you condense the text into a few key points?
<bot>: She broke up with her boyfriend and won't tell me anything about it. I asked her if she thinks I'd judge her and she said that I always judge her and that I, of all people, shouldn't.