If you can document (a receipt) that she purchased the cards from you then it's her problem IMHO.
If you did not already give her a receipt for her bulk card purchase, I suggest, as a courtesy, snail mail (AND use the $0.45 tracking service the usps offers) her a receipt. Type (or cut & paste via your pc) the angel policy(ies) of the stamp(s) you used in small print at the bottom of the receipt and keep that with your business records. This way she is aware of the policy, if she chooses to read her mail.
What a customer does with their purchase is their business. This is how current ebay sales of current SU merchandise are tolerated by SU: customers (but not demos) are allowed to rid themselves of their own merchandise any way they see fit.
You can try to blame your keyboard on your spelling errors - but it doesn't fly. You can not control what your customer does with his or her purchase. Put accountability where it belongs and in this case, it does
not belong with you, IMHO.
I have not done bulk sales of my cards; however, if I were to on the receipt (I do a receipt for ALL my card/craft sales as I pay sales tax via my business) at the bottom in small print I'd include a copy of the SU angel policy to cover my big butt.
If you are selling these cards I urge you to check the tax laws in your area. The $$ I was making prompted me to get a business license and it was not difficult at all.
P.S. I am not an attorney nor do I play one on tv.
Re-selling of cards
