too .to

Some vain people don't wear glasses. That is the relation.

too vain to wear glasses
too scared to fight a tiger
too heavy to float
too young to vote

[from dictionary.com http://dictionary.reference.com/browse/vain]

It's a very simple sentence. 'Too' in this case is used in the sense of 'too much' or 'more than necessary.' She has too much vanity(is 'too vain') to...etc.
She is concerned about her appearance.

Vain: too proud with ones appearance ,achievement .
So. If she is vain , how could her feel concerned with her appearance ? She should feel conceited , or confident, in a bad way .

Yes, but to say she is 'conceited' is the same as saying she is 'too vain.' The point is that because she is this way she will not wear glasses.

Ja..... I get it. Thank you