From my personal experience I found that a lot of girls seem to depreciate their appearance and think that they look worse than they actually do. I found that in general to overanalyze and worry is one of the stranger feminine traits. Indi had an interesting explanation of why this might be from scientific point of view some time back. I can't explain why some women do that. I think gentle positive support is the way to go with this.
Don't cry, don't regret and don't blame
Weak find the whip, willing find freedom
Towards the sun, carry your name
In warm hands you are given
Ask the wind for the way
Uncertainty's gone, your path will unravel
Accept all as it is and do not blame
God or the Devil
~Born to Live - Mavrik~