Women who have toned arms can still wear sleeveless dresses in their 50s. Otherwise, choose dresses that cover at least part of the upper arm. Three-quarter-length sleeves work well because they emphasize the slim wrists that petite women have and give them the opportunity to show off their wrists with pretty jewelry. Skirt lengths somewhere around the knee flatter the petite woman in her 50s.
Petite Valerie Bertinelli works at staying fit and her upper arms are not flabby, so she can get away with wearing a sleeveless dress, although I think this dress would have looked even better with short sleeves. Valerie's v-neckline would be flattering at any age, and she shows her stylish side with a trendy leopard print on her sleek pointed-toe pumps.