。
She waved her hand toward their table.
Literal
She [topic-は] hand [object-を] waving their table [object-を] indicated.
示す (しめす) means to show, indicate, or point out. She waved to draw attention to or indicate the location of their table. 手を振って chains the waving with the indicating — the wave itself serves as the gesture of indication. テーブルを示す is an interesting use of 示す for physical pointing rather than its more common abstract sense (to demonstrate, to show evidence).