fairies exi(s)t

You wake up in complete darkness. Standing before you is a girl who says she’s leaving you. You have no memory of who she is, but you feel that this stranger is important to you. She agrees to guide you through the memories you once shared.

The words “Goodbye” (ru:"Прощай") and “Wait” (ru:"Постой") have the same number of letters.
So… what will you say to Karen Smith?