It sounds like she might be trying to say that the funding source she has attached to PayPal is no longer valid, so even though payment has been initiated, it will fail or be rejected.

Was the payment an eCheque or instant payment, and what is the status of the payment in your PayPal account? If an echeque or credit card payment fails, you'll get notice, but if the payment is cancelled, no notice is sent at all. Sometimes a credit / debit card backed payment will go through as instant but then be rejected later on when the attempt to draw the funds is actually made, so keep that in mind as well. 

I'd double-check that the payment has fully cleared, and if there are any issues, you may be able to unmark as payment received an reissue the invoice, or generate one directly from PayPal and send it to her email address. If the payment has cleared fully, just explain that you have received cleared payment in full.