Its actually quite a recognised phenomenon, its just not talked about very often. Not sure why.
http://ideas.time.com/2012/10/04/womens-inhumanity-to-women/ http://www.huffingtonpost.com/dr-robert-lusson/womens-bias-a...
http://ideas.time.com/2012/10/04/womens-inhumanity-to-women/ http://www.huffingtonpost.com/dr-robert-lusson/womens-bias-a...
Alternatively, maybe it's talked about every day but amongst women.