What doesn't seem to have been pointed out is that these sweat-shop gift cards have already been bought and paid for. Companies sell these things precisely because they know that some of them won't get used - every unspent gift-card dollar is a gift to the company.
She should go to the stores and spend every cent on those cards. If she does a little research and uses some common sense, she can figure out which items are least-profitable for the company and may actually be loss-leaders - in that case, she can actually have her pound of flesh. But doing anything other than exchanging the full value of these cards for merchandise that cost the stores money to produce would be to support the companies she hates.
Buy the clothes and give them to the most repulsive homeless person you can. Drive their brand equity down while you're at it.
