Okay, now just to add my experience, have her place a deposit that will accurately reflect the size of the wedding.
In the past two weeks we have done two 10,000 weddings (no, not joking, I need a vacation and a massage) and both brides were very different.
The first claimed to have no budget but after two 500 centerpiece mock-ups she began to nickel and dime the heck out of us. Luckily we took a 2,000 deposit, so she was as invested as we were into developing her final plan.
The second probably could have gone even higher but we were able to discern what she wanted and price it out accordingly.
I PROMISE you, they have a budget. It may seem like after you have put a ton of time into developing one sort of event that they can actually afford 1/3 of it.
The deposit is the seal on the deal. If they seem at all shaken by more than a 200.00 deposit, then it is time to talk about the real nuts and bolts.
Every bride has big ideas, don't let those grow too big without some reality mixed in or you'll end up losing a bride or at least making it a painful process.