Perhaps there are two purposes? Perhaps there is an issue of covering the hair to symbolize the fact that she is married.
And beyond that, the normal laws of Tzinius of any clothing item apply – the fine line between between put to together and showy?
Is that a possibility, Oomis? “
Anything in life is possible. But unless we are certain that the covering hair is for reasons of tznius, we should not be telling that to people as absolute fact of halacha. It sounds good, but that does not make it the reason. If a woman is unmarried at age 45, does she not have to show dignity and tznius also?
BTW, the obligation to cover the hair (as I was taught ) comes after the Cjhosson and Kallah have been intimate. Some peope feel that being in the Yichud room for some amount of time qualifies also.
APY, for the record, there are Poskim who matir for divorced and widowed ladies to NOT cover their hair, so that they may find shidduchim. Not all such ladies continue to cover it.