Fangirl
Fangirls consist of the female fandom as opposed to males (fanboys). This is often an important distinction if their behavior is considered different than men.
The sterotypical fangirl is sometimes a mirror of a fanboy. She may be young, overly giddy, and excessively emotive, or surly, bitchy, and egotistical relative to her (presumed) appearance. She is often in the slash or yaoi fandom. Some argue these stereotypes come from the fanboy perception of women, which is often misogynistic or vindictive, especially if such women are not interested in them. Such conflict usually occurs when the subject matter they are equally interested in overlaps, such as shounen animanga (mostly male-aimed) invariably attracts yaoi fandom (mostly female-aimed). Another situation is where fangirls are in the minority and are more put off by the behavior of the male fandom itself, who are surprised women are interested in the subject matter. In contrast, fangirls tend to tolerate male minority in their interest fairly well.
Another trait of fangirls and fangirlism is the existance of BNFs, or Big Name Fans. These are usually the best or most prolific writers, artists or other creators of a fandom. BNF culture is particular to fangirls because of their extremely social and community orientened nature. The existance of these BNFs can often cause clashes among the fandom, especially with large or well known fandoms and BNFs. Harry Potter's Cassandra Claire is a good example.