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Well, just because she jumped the gun and hired an attorney, that does not give her a legal right to not accept the payment as on the Notice to Quit. So, yes. Your defense is she would not accept the payment. She legally needed to accept that payment and then if she had attorney fees associated with anything she could have sued you for those. Though she might not win because she had proceeded not in good faith that you would be able to pay within the alloted timeframe.
To answer your question, Yes. That is your defense.
If you have further questions, you can post them here and I will continue to assist. Otherwise, please remember to accept as that is how I get credit for my time and information in this matter. Thank you