We are living in a society that does not know the meaning of the word 'modesty'. Just look around you when you go to a public swimming pool or walk through the mall. Young women are bearing it all and everywhere you look, advertisers are encouraging them to do so.
I want to introduce you to an incredible resource I found that will help you teach your daughter about God's idea of modesty and why it is so important. The book "SecretKeeper; The Delicate Power of Modesty" was written by Dannah Gresh from www.PureFreedom.org. She explains in honest detail with scriptures and examples, the power of modesty. I can't tell you how many times I have stumbled through trying to have this conversation with my daughter, buy Dannah explains it so much better!
It seems the conversation about modesty never happens until we are in the middle of a store and begin arguing about why I won't let her buy an item of clothing. Then both of us are emotional and heated. This book has really helped us sit down and have a reasonable, honest conversation about it without being "in the moment" of shopping.
Having discussions after each chapter has really helped us understanding each other. Shopping still isn't easy, because the world dictates the styles of clothes that are out there, but we both know we just have to look a little harder to find things that are appropriate for her age.
Spend some time checking out the SecretKeeper website. I think you will find it very helpful for both of you!