Don't budge...if she wants your cakes..she will have to pay for your time to decorate...if she still is trowing a hissy fit..let her go down the street to see what kind of deals she can for what she is wanting. The price she is quoting may be for a very plain cake that won't take the time the design she is requesting.
Also, if you budge, the message will get out to the new brides that if they push, they can get really sweet deals from you and that is not what type of business you are running...especially if you are wanting to stay in business....
STAY FIRM and DON'T BUDGE
Just my 2 cents