I think that women are often lumped into categories - single gals, or soccer moms, or career women, or women of a certain age. For some reason our society wants women to wear labels, and not only on their clothes.
I don't think the role of style is different for a woman of any age. Style, to me, is about experimenting with what gives you pleasure, a joyous expression of imagination. I emphasize joyous because too much is written about fashion that takes the pleasure away - clothes that make you look thinner or clothes that make you look younger or, horrors, clothes that make other people envy you or that - double horrors - are "age appropriate".
For me, style is about forgetting the rules or creating new ones.
I like clothes that stimulate the senses, fashion that is both exquisite and intellectual.