So I've had uh, some questions about my sexuality lately, and I've been reading forums by women in the same situation. The answer is that a lot of people, including researchers and often women themselves, don't understand female sexuality. Most women are strictly heterosexual. There's a surprising number of women who are clearly heterosexual from the way they talk about men and women (this is an amusing example that I found) but convince themselves that they are lesbians.

Women are apparently physically aroused by porn of damn near everything. One of those studies showing that all women are bisexual also showed that women are turned on by monkeys having sex. I don't know why this is, but it does show that using physical arousal as a measure of attraction for women is not going to give you very good results (or, alternatively, that women are all bisexual AND attracted to monkeys, but this seems less likely). My guess would be that it's a defense mechanism against rape - if sex is going to happen to you anyways, may as well respond physically, to prevent physical damage and pain.

Female sexuality involves, like /u/xQueen-Bx said, wanting to be the object of desire of someone you find attractive, not being attracted TO them. A lot of straight women think they are bisexual when they really just mean "I think women are nice to look at". These women do not want to be desired by and seduced by a woman. They might be watching lesbian porn, but they aren't interested in the lesbian version of stories like 50 Shades of Grey - that's a better measure of whether or not they're actually attracted to women than watching porn, IMO.