the friend decides to enter the house at 4am and take photos of you sleeping.
That's an oddly specific example Glass, care to enlighten us further on your creepy friends? hahaha
Based on no legal knowledge or background.
If old mate went into her phone as he suspected she was cheating on him, found evidence, screen shotted it and sent it to himself or a family member for "safe keeping" and he didn't try to ruin her by naming and shaming her on a public forum such as Facebook, he won't get into any trouble and she should reconsider how she handles herself in future relationships.
Every man and their dog that's going through Family Court/ DV Court/Criminal Court has screenshots from conversations on their ex's phone. (or is it just me??) Nobody blinks an eye.
Not a lawyer just my 2c