Is Sexuality Fluid???

Sexuality is Fluid....
I don't mean like: you wake up and turn gay (p.s. no one “turns gay”—that phrase kills me)
I was attracted to this Lesbian who was very masculine..Would I act on it? Iono but i remember forgetting she was a she and just concentrating on how sexy she was…
when it comes down to it attraction is not about parts, but rather the essence of the person standing in front of you!

This is a post from How to be Nola Darling (deux) a great tumblr site that I follow.  It got me to thinking coupled with a question about my sexuality from a friend lately.  The fact that I have never dated I have been asked on a few occasions (from a few bold people) was I a lesbian. Question took me off guard, but it also made me think.

I can say no I am not a lesbian, but I can see how sexuality can be fluid. Have I ever been attracted to a woman, yes, but that woman had very masculine traits, and some of my attraction was can I say....complicated, it was more about the person than the gender. I love men and what I desire when I am with a man that I am attracted to, but can't say the same thing about a woman. But I totally agree with his last statement....the essence of the person standing in front of you.

What are your thoughts on the subject?