Low quality product, bad attitude, not refunding

After designing and printing business cards for more than a decade, I came across a special for 500 cards for R220. I ordered 2 sets, with specific instructions of the size and edging etc. Each set had different QR codes on them. Charmaine told me that she uses GLOSS paper. Twice, I received proofs with the incorrect size & spacing. The last proof looked the same, so I assumed her program set it up in that way. Being unsure, I attached a PDF file and indicated that the final product should match my PDF file. Upon receiving the cards, both cards had identical QR codes, the logos were off centre, the whole layout was made smaller and the paper was a dull semi-gloss. Naturally not I, nor my clients were happy and I was laughed at. They wanted their money back for the low quality product. I now have to redo them at my normal supplier at my own cost. Upon confronting Charmaine, she kept on insisting that I approved the proof and that she was not to blame for it all. She offered to give back only half of my money. I think it is very unfair if you supply a bad quality product which you can't use and which does not match what you wanted, and still take money for it.