Your total weight loss will depend on your initial weight, percentage of body fat, body type and other factors, such as when you begin dieting, but you shouldn't ever try to lose more than 1/2 a pound to 2 pounds per week. Anything more than that, and you'll just be burning off water weight or lean muscle mass (which is directly related to your metabolism), neither one of which is beneficial and can actually make losing weight even more difficult.
And it gets worse. Losing more than 2 pounds per week will result in low energy, low blood sugar, fatigue and dehydration -- none of which are ideal conditions when you're planning a wedding. Plus, all the weight you lost is almost guaranteed to come back as soon as you stop dieting.
However, don't be too alarmed if your diet and exercise regimens help you start shedding 3, 4 or even more pounds per week. Women who weigh more to begin with may see rapid loss at first, but after a few weeks, the weight loss will plateau to a more average (and realistic) number.