if you remember her riddles, she asked you a few that the answer was a single letter. those letters can be arranged in order to give her the answer she wants. if you don't remember what the letters were, post a reply here and ill get back to you.
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Don't worry too much. Even if you don't remember who Kate is, or you have already answered her riddles and can't remember the answers, a quick google search or asking for help here will get you sorted out. I have a list of her riddles handy and know which ones are for solving her final riddle. I can just give them to you again if that's what you need.