Most people clean up too fast. A look hangs there, and somebody coughs, jokes, checks a purse, asks about work. The room gets bailed out before anyone has to sit with what happened.
She does not bail it out. A comment lands at the table and the quiet stays. She takes a sip. Looks back. Lets him deal with the second he created.
It is awkward, but not in the normal clumsy way. More like an unread message sitting on the screen. Nobody has said anything wrong, so nobody can fix it. That is why he keeps thinking about it later.