In writing historical fiction one has to be aware of the changing styles of women's dress over the centuries, and what fabrics and colours might be available at different times. When did the styles associated with the Regency appear? When were crinolines first worn? When exactly in the 1920s did short skirts appear, and when did hemlines drop again?
And there is fashion, and there is what people actually wore. And for a novelist, a character's dress can be used to reveal information about him or her to the reader.
How quickly would a young woman become aware of the latest styles? If she was a servant in London or a factory girl in Manchester, probably quite quickly. If she lived on a smallholding in a remote part of Cumberland, it might take her a while longer.
It's not necessary, in fact it's probably unrealistic, for a character to be wearing whatever is in the latest fashion plates. Only the most wealthy and fashion conscious would be always up to date with the latest styles. Some might have the money but be uninterested in fashion. Most girls and women, if they could afford it, might buy one or two new items every year, or every winter and summer, and have a mix of new and older clothing. Some might rarely, or never, have new clothes.
Is it practical or appropriate for the character to be wearing the latest fashion? I have a character who is a young woman in the late 1870s. The latest fashion in ladies' day and evening dress then was narrow skirts with long trains and lots of elaborate trimming.
My character would not have worn a dress like that, for several reasons. I had to search to find out what she would have worn. Artists and photographers who depicted street life and domestic scenes are the best resource for this type of research.