The solution is to give her FAIR options and let her decide. I think the best options that show you are doing everything to cam to accomodate her is to offer:
a) a discounted photoshoot with her dad however she wants. I say discounted off your normal rates, not free, but for cost(time/materials) +a little profit on top like say 50% of your regular profit. So say your normal rate is $100/hour and out of that $50 is roughly cost (time) and the other $50 is profit, do it for $75/hour. Something fair.
b) offer to refund your profit portion of your rates. From your post above it seemed you charged $1250 for the wedding, at 4 photographers I would say cost would be $200/photographer=$800, so offer to refund the remaining 450, so that you take no profit..... and she gets no photos at all. Basically like cancelling the contract for the wedding day to begin with.
c) offer a few extra 8x10's or something
What you must not do is refund her half the money like she wants. Basically she is trying to re-negotiate the contract after the fact and if you let this happen it will hurt all photographers in the longrun as more will expect to be able to do this.
Think about it. If I pay $50,000 for a wedding at a luxury hotel, can I go back the day after the wedding and say the place wasn't worth $50k and I want to only pay $25k??? No they would laugh. THat is what she is trying to do to you. You agreed on a price, she accepted the contract for that price, you honoured your end of the contract, you get the money.
There is nothing she can do about it, she owes you the money and would lose in a second in court. And regardless of what you do, she will never become a positive reference. You could give her all her money back and she will still mention how you missed "the most important shot"

