My daughgter and her fiance are getting married at WDW next June (2012) and we're starting the process of pricing, etc. She is a little older than your daughter, and what I did (because you can just go crazy with the costs) was told her I would give her $X,XXX towards the wedding -- anything above and beyond that was on her and her fiance. So this forces her to look for the best "deals" -- not getting married inside a theme park means she can use an outside photographer -- Disney photogs have a minimum charge. There are lots of other variables involved in choosing a package, etc.
I do know that if you try to get married on WDW property and it is a wedding or ceremony not sanctiioned by DFTW, you could possibly be banned from WDW for life. Not something I would even want to chance -- not that we would.
I do have to admit that I gave her a budget towards her wedding dress, but I ended up caving on that -- spent $500 more than I said I would -- but she is my only child and we've already paid off those college debts.
Of course, she could take the money and use it to put down a very nice down payment on a house, but she has her heart set on a WDW wedding. But what does one expect when you've taken her to WDW every year since she was 3 years old.
I did set a budget for the wedding itself because I would like to retire in the future and not want to be several thousands of dollars in debt due to a wedding.
I also have to add that the prices that DFTW charges are not out of the ordinary. My sister does catering part-time and I've seen some of the costs associated with some of the weddings she's worked.