According to the 'Jane Austen Handbook', a bride's father would be expected to buy enough new clothes to last her a year after her wedding. This would be to spare her husband the expense of buying these items during that period.

This makes sense, because setting up home for the first time is an expensive business. Also, as we see in another JA novel, a new bride is a socially important person in her community for a time after her marriage and would surely want to look her best at this time.

I understand the dress a woman wore to be married in would often be used as a 'best' dress for social occasions afterwards.

Mr Bennet refuses to buy Lydia clothes because he doesn't want to show her any sign of affection. Given that he's never given her any sign of affection or regard during the course of the novel, how is Lydia supposed to notice the intended rebuke?