Use the adverb fashionably to describe something that's done in a stylish way. If your mom is famous for dressing fashionably, she always looks chic and modern.
The hairstyle that a teenager thinks is fashionably uneven might look outdated in just a few years. If it's important to you that you dress fashionably, you'll inevitably have to spend a lot of money on clothes and shoes. And if you have friends who always arrive at parties fashionably late, it means that they believe it's trendy to show up an hour after everyone else does.