Here is a great website for her to look at (with you maybe?) to see how guys look at girls from a modesty perspective. Maybe it will show her what she needs/wants to know? I am so thankful we stuck to our parental guns with all three of our daughters - one, to this day, is fighting the modesty issue, another, usually dresses modestly and the third is always modest. When she's old enough to understand that you did it for her own well being she'll thank you - ours have! :)
http://www.therebelution.com/modestysurvey/browse