I know how heavy that gut feeling can be. It is incredibly draining when trust starts to wobble.
Usually, the biggest signs aren’t specific apps, but changes in behavior. Is she angling the screen away, taking the phone to the bathroom every time, or getting defensive when you ask simple questions? On Androids, features like “Secure Folder” or turning off lock-screen notifications for apps like WhatsApp or Snapchat are common ways people hide activity.
However, hunting for “proof” can quickly become an obsession that hurts you more than the truth does. If you can, try to have an honest conversation about your fears first. Protecting your own peace of mind is just as important as finding answers.