Didn't have my daughter till I was 45, she's now 17, has lots of friends and always tells me how I look, it can range from, scruffy (when I'm wearing jeans walking the dogs or cleaning out the rabbits), old, (when I put on something I think fitting for my age) and great (when I make an effort and dress as I would if I didn't have work, animals and a son and daughter to clear up after. Her friends tell her I dress better than their parents so listen to the young ones - they won't let you get away with anything.
Please only yourself! You have probably spent years taking care of others, so now dress and groom yourself exactly as you wish. Let others think what they will; to impose the chore of "looking younger" or "always looking your best" on an older woman is requiring that she spend yet more time pleasing others or meeting others' standards. Honey, do whatever you want; you've earned it!
Dress for your body shape (your real body -- not the one you wished you had). Dress in colours that flatter your skin tone, but keep it simple/monochromatic (save the flare for tasteful accessories like scarves, jewelry). Add one amazing accessory -- be it a handbag, pair of shoes, necklace or scarf; do NOT go overboard. Don't confuse elegance with labels or logos -- a well-made unique piece is usually more elegant than dripping in Chanel logos! Avoid looking too matchy-matchy -- like you bought an entire line at one store; you could come across more fashion victim than fashion icon.
Pick a fashion icon you love and copy what she wears until you feel comfortable adding your own style. Audrey Hepburn is fantastic for something like this--classic white shirts, turtlenecks, black pants and flats or pretty dresses nipped in at the waist. The clothes she wore look good on most body types with just a little alteration.
An older woman, always looks good when groomed, and wearing good quality(the best you can afford) clothing that is stylish, simple and well tailored. A well cut blazer style jacket, with slacks and skirt can then be made modern and younger, with t-shirts, blouses and ONE new fashion item. This may be a belt in a bright colour or a good pair of jeans, and modern style shoes and bag. This will stop you from looking 'like a Nana', and be comfortable at the same time. Also, tone down your makeup if you have always worn it, or start wearing a little if you haven't...you will need subtle colouring around your face, to stop you looking washed out and pale.
Listen to the teenagers. They'll let you know if you're dressing too old or young for your years and will also truthfully tell you if you look good. Obviously we're talking about smartly dressed youngsters and ones whose clothes you'd love to wear if only you were their age. You can always take something from their look that you can adapt to suit you.
For the older people I would suggest kaftans, big belts... but best of all is the accessories. You can glam anything up with long necklaces, bangles etc. Try not to fall in to buying things to big or to small and i would stick to the neutral colours for elegant styling rather than the fashion!
Try, but not too hard. Remember there's a fine line between sexy and slapper when over 40, so no bare midriffs off the beach, tattoos, goth eye makeup. If in doubt, ask your son or any other handy yoof!
Cleanse, tone and moisturise twice everyday this will keep your skin looking fresh.
Little things like hands also give age away so make sure you use handcream everyday.
I would say always make an effort to do your make-up and paint your nails. That always makes me feel good!
Remember as they say: Beauty grows with age!