Friend doesn't exist on psn

Well I've been trying to add a friend of mines that has a psn. When I enter her id it says she doesnt exist o-o. She says she has sent me messages and I havent gotten a single one of them. Anyone wanna take a shot at this?

She didn't give you her real account ?

Its the real one. I've seen it personally

why not go to their place and add yourself

Tried that wont let me

EDIT: Is there a way to search for someones psn online?

Parental Block ?

and to answer your edit you can try entering her ID here:

http://www.yourgamercards.net/generators/trophy