<human>: Give me the gist of the text in a nutshell

I got together with her about a week ago, it's a long-distance relationship, so we'ren ot able to see each other every week. This weekend, she spent the night with her ex (which itself is unusual for me, but they seem to be good friends), but she didn't tell him that she has a new boyfriend, and after I asked her to tell him, or at least tell me why she doesn't want to tell him, she didn't answer anything useful (just "I don't know" or "Okay..." or something).

I don't know how to react to this. If she'd cheat on me, she could've tell me that she told him, but she didn't. I'm shaking right now, because I just don't know what to do, and I really, really like her, but I don't want it to be this way.
<bot>: My girlfriend spent the night with her ex (they're friends), but she said she don't want to tell him that she has a new boyfriend.