I think they were friends on the level Spike implies they were friends. She was nice to him, even when she had no reason to. And he clearly enjoys the attention she lays on him in Lovers Walk. If Buffy hadn't showed up, I imagine he could have sat there drinking cocoa and marshmallows for hours, telling her about all his sorrows.
This implies friendship how? The story doesn't run on imagination. You could just as well imagine he get bored and kill her. Their convo lasted exactly as long as it took for Buffy to get from the school to her house.
He subsequently never bothers going there again until S5 when he's there to con Buffy into his not-a-date. How great friends were they?