I have to disagree there,Mandy.

I do agree with you that clothing is rarely mentioned in her novels, (and when JA does mention clothing it is usually to make a specific point),but her letters are often full of mentions of clothing details.Because often she was asking Cassandra to carry out commissions for her and vice versa.

Penelope Byrne in her book Jane Austen and Fashion states:

Although the references to dress and needlework are comparatively few in her novels there are many in the letters of Jane Austen and together with those that appear in the novels enough information is provided to give an interesting and often vivid picture of the clothes worn during the period of her lifetimepage 16

I think most costume historians would agree that contemporary reports of clothing like those found in great number in JA's letters, and in similar correspondence by Mrs Delaney for example help tremendously with regard to research of fabric and the clothes worn during this period.