Emphasize the one day vs your future factor. Of course she wants it to be the most special day, but does she really want it to cost what you both earn in one year? Five years down the line, is she really going to regret not having the most lavish amount of flowers? Let me tell you something: I have never ONCE heard anyone lament that they skimped on flowers at their wedding. I HAVE heard couples lament how much they spent on their wedding. Guests do notice the quality of the food and whether there's an open bar. Decide what's most important to provide in your event, and research how you can save on everything. If you do more of a DIY reception, sometimes you can buy your own booze at a Best Buy or some discounter like that...

All brides get crazy planning their wedding and for some reason the budget goes right out the window. Maybe just explain to her that you know how important it is to have everything perfect but the most important part of the day is you guys, not the flowers or food.. or whatever. The day will go by so fast, you will barely taste the food or talk to anyone before it's over then your left with a huge bill. So, I would say you have to be honest.. it's not in either of your best interests to spend a ton of money on a huge party when you could save for your future together....esp. since that will last much longer than one day....