What is combing hair all about in folk songs?

I know imagery is representational in a lot of cases, and I can't beleive this isn't one of them, but no one I've asked seems to be able to tell me what it might mean.

The songs I know of with it in, Tam Lin and another, can't remember the name, genberally have the lady doing the deed before she goes somewhere, or a dramatic event happens, does she just want to look beautiful, or is it, as I suspect, a little deeper than that?

Help with theories, hard facts and general refferences to other songs with the act included would be appreciated.

Thanks Fay xx

Also, it's generally a silver comb, does that make a diffeence?