I struggle with this. I don't want to dress like a granny or a frump, but I don't want to look pathetic and delusional either.
When I think someone is very age inappropriate, it is usually due to there being an eye jarring and attention grabbing contrast. I once saw a woman in her 70s (judged by wrinkles and loose skin, on abundant display) wearing clothing and bleached blonde long hair in an high, I Dream of Jeannie pony tail, and makeup (outrageous false eyelashes and incredible amounts of black eyeliner) that would have registered "street walker" on a 20 year old. That was just very, very sad. She was getting plenty of attention all right, but it was horror, not attraction.
I know a woman who dresses appropriately for her age (although she looks rather older than her age, because she smokes) but not so much her body shape. Plus, she walks like her feet hurt, which is very aging. Not an extreme case, by any means, but I tend to do a bit of mental making over when I see her.
I think that virtually any trend can be styled in an age-appropriate way. I think the biggest red flag is too much skin on display, and sporting multiple trends at once. Let's see: cold shoulder top, extreme platform shoes, tiny white short-shorts AND a hot pink hair extension with feather earrings--on a 50 year old--no--that would flunk my mutton as lamb test. But, with the exception of the shorts which wouldn't look nice on my body, I could probably age-appropriately handle and style any ONE of those trendy items.
