I think your confusion is about when the effects of an attack are done.
They are done during your turn.
You don't end your turn until all attack effects and effects triggered by that are resolved, including any prize cards that have to be taken and KO'd Pokemon that have to be replaced.
Then, once all that is done, your turn ends and you move into the "between turns" phase.
So Impersonate and Cynthia's Feelings are performed and resolved during your turn.