What’s the difference between old-fashioned, out of fashion, unfashionable and outdated?
She wears old-fashioned clothes.
She wears unfashionable clothes.
She wears outdated clothes.
The clothes she wears are out of fashion.
She wears clothes that were fashionable a long time ago.
She wears clothes that were never fashionable.
She wears clothes that were fashionable when she bought them.
She wears clothes that were suitable when she bought them but no longer are.
That last one sounds a little awkward. I don't know how clothes could become unsuitable except by becoming unfashionable (they could be no longer appropriate for the age or maturity of the wearer, but that isn't what "outdated" refers to) but the word makes more sense when applied to a subject that has an object measure of suitability. For example, a medical treatment (or other technical product or service) that was cutting edge in 1980 might be "outdated" now.
Her attire is neither modern nor fashionable.
Most people would not wear what she's wearing.
Her wardrobe is not suitable for a modern office.
Her microskirt has fallen out of favor with American women.