To me, the key thing is that she did not respond to your e-mails. Therefore, my inclination would have been to send the un-cut yardage at the full rate. If you had done that, she would have had no right to complain. I understand your reasons and that you are not obliged to know all the import fee rigamarole for everywhere, but you had all legal & moral right on your side by sending it in one package. By doing it the way you did, you left yourselves vulnerable to the customer's displeasure.
Ooops, I need to add a p.s. I see in an earlier comment that the shipping price would have been $15.00 more than she had agreed to? I don't understand that, but that doesn't matter. It does change my response to your question. I would not have sent the fabric without getting further instructions from her.
You are wise to do this research to avoid a similar situation in the future.