Girl talk is the stereotypical, female version of Guy Talk. You know, guys talk about cars, sports, the stock market, the hot babe who lives down the street, and girls talk about makeup, their clothes, recipes, their kids, the fight they had with their husband yesterday, etc.
In reality, everyone talks about everything. I personally love to talk about ideas. :p
Edit - my female friends and I discuss current events, politics, work matters, the politics at work, our mutual hobbies, our children, and give each other news of the people that we know. IF we ever talk about fashion, it will be a two minute comment, where one will tell the other about a new find, if she recently bought something. We never, and I mean NEVER talk about makeup. Most of my friends don't wear any. They don't need to, they're beautiful enough as they are!
