[Quiet Man Cometh]

Turning on my objective brain, I'd say she was being cheap. It's your mirror to sell, therefore you set the price. If she wants to buy it she can, at the price you are selling. If you said that you'd give her the $15 from the sale of the mirror then it makes sense to knock that $15 off the price for selling to her, but if setting the price of the mirror was never part of the deal in the first place, then she doesn't get to gripe about it. That's my view but I'm a pick with money.