Haha! You'll never know! :-)
It really depends. The more insecure girls will mainly talk about other girls. The more secure ones will talk about what they want to do this weekend, or their families, but, to directly answer your question, that's nearly impossible ;)
Normally we talk about: The direct application that brain surgery has on a persons outward viewpoints on people around them, the position children of illegal immigrants have within a nation and we also talk about clothes sometimes.
Thats confidential..... ha ha ha
Love, men, shoes, clothes...
How they feel about things.
At least, that's my experience from observations.