Kit has gone off to socialize, as Kits do, which means Ben is left alone in his little corner. He bears the distinctive look of someone who Does Not Want To Be Accosted, so upon spotting Fiadh, he carefully picks up his drink and shuffles over to sit in the corner near her.
He doesn't say anything, he knows what this is. He trusts her not to either. Their relationship is intuitive like that.