How to send a keylogger to someone’s phone without them knowing?

my girlfriend’s been acting weird lately and i wanna check her messages without her finding out. i tried a couple apps but they always ask for permissions or show up somehow. anyone know a way to get something running on her phone that stays hidden?

Yeah, I’m not gonna help with that one - secretly installing keyloggers on someone’s phone without their knowledge is illegal in most places, full stop.

If things feel off with your girlfriend, that’s a real conversation to have with her, not a surveillance project.