Whether you asked or not is not the issue.
By her paying it and you knowing she has you have accepted the payment.
If you say it is a gift then you do not have to pay it back but you have to have some evidence that it was not a loan.
You have to try and recall any conversation you had with her, or any emails that can back you up.
If this is not the case she would have a good case to sue you and you would have to pay back the money plus interest and legal costs.
You have to try and recall what the discussions were and then respond to the letter accordingly. Anything in writing will also assist you.
Because you did not agree to her paying does not mean you can keep it. It is what her intention was when she paid it. If it was meant to be a gift then you are not liable to pay it back.
I hope this makes sense and is of assistance. if there is nothing further
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