Question

So... still no clarification on this subject, huh. I'm hoping Eos or a transgender will have some input.

Lulz. Does Eos have a magical understanding of sexuality denied to others?

Anyway, your question isn't a real question.
It's inherently flawed because it's seeking a binary answer on a subject that's naturally spectral.

First of all, to define someone's sexuality by one sexual encounter is fairly juvenile.
A female fooling around with another female doesn't magically transform them into lesbians anymore than a gay man fooling around with a female would make that man straight.

A hypothetical encounter between two individuals sharing genitalia could result from either realized attraction or sheer curiosity.
Out of the encounter, either individual could find him/herself could wind of with any multitude of conclusions.
Maybe his/her entire life has been a lie and he/she is a homosexual.
Maybe he/she is actually attracted to both genders (bisexual).
Maybe it will just be a one-time thing that's never again pursued.
These are just a few examples that certainly don't delineate all possibilities, but even these small examples have issues such as "where do you draw the line between homosexual, bisexual, and heterosexual?"

Again, spectrum, but the spectrum goes deeper than that because, as this thread has already demonstrated, defining one's gender isn't entirely an objective matter.
The common stance is to define it by a person's physical traits, but others have already mentioned that there are plenty who determine gender by what a person was born as, how a person acts, or even what any individual considers his/herself.

Since the definition of one's sexual orientation unavoidably relies on the definition of sexual identity and because sexual identity isn't a clearly defined, it's impossible to clearly define sexual orientation.

"Translation squirms in the presence of the exotic. The (language) which I speak here imposes itself. It is an outside frame of reference, a particular system. Dangers lurk in all systems. Systems incorporate the unexamined beliefs of their creators. Adopt a system, accept its beliefs, and you help strengthen the resistance to change."

I would ask myself: Am I attracted to this person because of their genitalia (which is female) or because of their personality (which is male)?

I think being attracted to someone because of their genitalia would be considered a fetish.
Most people don't crawl into bed with someone because they've seen what's in between the other person's legs and found it to die for.

dunno, in some lesbian relationships (and gay ones too) one takes the role of the submissive one, and the other takes the other role, their personality doesn't seem to me to be the way to categorize this.

i'm wondering how the state sees this actually.

Any given state would have a different definition. Not that it matters since laws concerning such things are rarely scientifically based. Popular opinion and all that.

I do find it sad that you limit someone's personality to whether they are aggressive or passive.
I assure you that most individuals I've met are far more complex.

By your example wouldn't it be considered mutual masturbation as they can't genuinely have intercourse by natural means?

That's a whole different subject, but I appreciate your line of thinking.