Haha, I always had problems with saying no to people - my advice is just to be really forgetful. If she asks for your Psych notes again, say, "Sure, of course! Can I give them to you tomorrow?" Then 'forget'. If she asks again, say, "Oh, silly me, I'll bring them tomorrow!" Rinse, and repeat. Eventually she'll just give up and go somewhere else. Remember - she can't make you give them to her. It's your work. She's just seeing how far she can push you.
Good luck!