[Silence]

To answer your questions,

1. You can't, unless you just stumble upon them.

2. Antivirus, unless its FUD, then turn off the WIFI on the PC or Phone and backup. Then you can reset to factory settings.

3. There are ways you can reverse engineer to find the person, but if you don't know how I would suggest not doing it.

4. If you find the person, report them, don't harm them.

She said she didn't download anything from anyone expect pictures so, assuming FUD.