Welcome to Android Central! MyOS is ZTE's user interface. com.myos.camera is the system app for the camera. It's fine -- may I suggest not snooping on another person's phone, even if it's a significant other.
Keep in mind that a person's Google account activity will often show various app activity, even if the person is not actively using those apps, because it's common for apps to periodically ping a user's Google account to refresh data.
I'm closing this thread because nothing more needs to be said about looking at someone else's data.