。
She gave him a quick little bow.
Literal
She [topic-は] him [to-に] with-a-bobbing-motion bow [object-を] did.
ぴょこん is a 擬態語 (state mimetic) for a quick, bouncing motion — perfect for a small, abrupt bow that goes down and pops back up. The と after the mimetic is the adverbial と modifying the verb. Together: a charming, animated bow rather than a deep formal one — befitting children, casual greetings, or playful interactions. お辞儀 (bowing) is the universal Japanese greeting gesture, with depth and duration calibrated to formality.