Some are rankled by Bree being confirmed in part because she is a woman.  Her gender is actually a qualification, since women often have a different experience with the built environment. Go back just a few years and read the Scientific American article on how women deal with transportation. http://www.scientificamerican.com/article/getting-more-bicyclists-on-the-road/
As far as being young, sure, she has a lot to learn. I also believe that younger people (of which I was once one), offer original thinking uncluttered by an ossified mind. 
I surmise that the photo of a young woman riding her bike and a story of that same woman being appointed by disliked council members immediately set off a search by some people for confirmation that this was a bad appointment. 
Seems to me that anyone with better ideas should apply themselves for such positions. Or other similar positions. Or is it, "I would not want to be part of a committee that would have me as a member"?