I recently saw my LTR has been texting this guy for a few days. she initiated 2 conversations and then invited him and 2 other guys from the same class to hangout at a theme park for Halloween.

she has brought this theme park up for us to go, but never mentioned other people or this specific hang out. when I brought it up (we were looking at her phone together) she didn't explain and was trying to change the subject or not talk about it (at least it felt like it, I could have misinterpreted or don't remember clearly)

I know this isn't acceptable behavior but I have no idea what to do next. I'm not going to confront her because that shit won't do anything so I'm stuck between demoting her to plate only, hard nexting her completely or using a little more dread. thanks for any and all help