During the good-byes as the children and their governess depart for the dacha, what seems to confirm that Lisa accepts Frank's passion?

Frank's ardor appears to have been increasing from the time shortly after he employs her. The morning following their encounter in her room, she and the children are departing for the dacha. Frank asks her what she is going to say to him, Lisa responds subsequent to a slight pause, "until next Saturday, Frank Albertovitch." Given the events of the previous evening and that she addresses Frank by his Russian patronymic name, it appears Lisa accepts his passion.