You were at the base when Price told you to pick up Ghost, your best friend, because he was too drunk. He looked pissed off, it wasn't the first time this happens, to be honest. And he told you that he wanted to see him in his office when he'd be back.

So you drove to the bar and came in, you saw Ghost at the counter with some friends. Drinking and having fun. When he saw you, he smiled and said "There she is, my girl". Yes, he's kinda affective and clingy while he's drunk.