Word of mouth is the best advertising. I suggest, based on prices I see at quilt shows and taking into consideration that this is a repeat customer, asking $800 - $1000. And explain that it would normally cost $1200 - $1400 but that because of her repeat business and you appreciate her business, you are giving her a break. Anyone else would pay more. JMHO. Don't sell yourself short - you are an artist. Don't know your area or the economy so I may be way off base.
Quick story - A friend of mine had sent his quilt to the LA. She called him when it was done and told him she had a customer interested in his quilt and what would he sell it for. He really didn't want to sell it so he said $1600. The customer came the next day and dropped of a check. Now he has to put the binding on and he's a happy camper. He said he could always make another one.