How can you tell if someone is mentally ill or just mean & trying to control!

I have a friend who makes good money but it not educated. So she works with professionals often & she has had people resent that she makes so much money when they have Phds. & don't make that much. I have heard twice that people have verbally attacked her. Recently a man came to her door & told her not to take a certain job cause his wife didn't want her there. He called her names saying she was a narcissist, mooched off of others, etc. She hasn't mooched off others but she borrowed money to take some time off from work & teach herself what she is able to do now.

So another friend said this man was a bully & sounded like a paranoid schizophrenic. When we was going nuts at my friends house she got her cell phone & called his wife. He then went home & got on the phone & she heard him say "this phone is being monitored".

She feels sympathy if he is sick but if not she needs to hold a firm ground so she is not being bullied. So how does one tell? He is addicted to Fox News & on medication for some health issues. thank you.