That kind of sudden privacy switch would mess with my head too. A few years ago my girlfriend randomly locked every app on her phone after never caring about it before. Same vague answers when I asked. I ended up trying a monitoring tool just to see if something weird was actually going on. I used https://spybubblepro.com/ and it basically lets you check things like messages, call logs, and general phone activity from a dashboard. In my case it turned out she was just planning a surprise trip with friends, nothing shady. But at least it stopped the constant guessing in my head. Sometimes behavior changes have simple reasons, but yeah… curiosity can really eat at you until you know.