Go totally pro on her. Tell her 'I'm sorry, you didn't contact me about
scheduling an appearance, we haven't
gone over logistics and you haven't even
signed a contract. If I HAD been properly scheduled, I would have g
iven you advertising materials to be included in your promotions. If you want me to appear at your function with this little notice,
my fee is doubled (YES, I said DOUBLED); you will need to
provide proof of event insurance; and I will
need the following items upon my arrival (outline what you want for lunch, a bucket of iced bottles of water, etc...). You shouldn't have told anyone I was already going to be there without a signed contract, and at this point, I am under no obligation to appear at your event.
And a friend would have already known this.'
As for "great exposure for you" (I get that all the time when asked to photograph), say 'I have all the exposure I need, thank you, and when I need more exposure, my marketing team handles that. Have a nice day!

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