What are age-appropriate hair accessories?

I'm writing a story about a 20 something girl who visits a Japanese inhabited Planet. She dresses up in a kimono for the first time and I was wondering if it would be appropriate for her to wear a bough of Wisteria in her hair, a silk hair accessory of course. I'm just wondering, is that something only Geisha wear? Or only girls for her coming of age ceremony? She's a princess and they have a formal meal, but it's not a party or special occasion or anything. Should I adorn her hair with something simpler like a silver fan or hair clip or something instead? I would really appreciate the advice, thanks.

Anything can happen in "a Japanese inhabited Planet."

I think you're referring to kanzashi:

http://en.wikipedia.org/wiki/Kanzashi

http://thekyotoproject.org/english/kanzashi/

Thank you for the new reference material and the opinions. I now have new additions to my research favorites. As well as a good idea of what to put in my character's hair. Arigatougozaimasu!