When Buffy sees Angel and she is admonishing him for not letting her know he was down in Sunnydale, she says:
Buffy: What is it? You can see me, but I can't see you? What are we playing here?
In the Buffy the Vampire Slayer episode "Pangs," Giles says the same thing to Angel when Angel comes to Sunnydale.
Giles: It's not fair. You know that's what she'd say. You can see her and she can't see you.