This is something that I can see both sides of the debate on. She loved Oz, no doubt about it, and is not openly regretful of her past romantic & sexual attractions, and occasionally jokingly references them. However, looking at her dreams in 'Restless', she seems to have a fear of her 'outfit' reverting to her school one, and there's a subtext that she equates her lesbian identity with her 'mature persona, hence she thinks of herself as *not* being bi.
I'm friends with someone whose girlfriend went through a similar trajectory, so it doesn't seem too jarring to me - unlike the melodramatic end to season 6, which fell into the 'dead lesbian/angry grieving lesbian' trope a bit too heavily!
This is how I view it. Sexual identities evolve, especially back when we were all supposed to be straight. It often takes meeting "the one" to shatter our confusion - that or becoming comfortable in our skin.
Had i grown up now, i am sure i would have dated around the genders freely. Not because I am a slut but bc my heart and my physical attraction belongs to a person not a gender.
I knew all along I was attracted to both genders. As someone in the church at the time, i had a hard time allowing myself same sex friendships. It was too confusing. As i am kind of androgynous, i also had little in common with legislated femininity as presented by the church - so could not relate to many women in church.
So it was years in recovery and comfort in my skin and being with two men (one of whom died) who i freely told i was attracted to women...
Then someone insulted my late god father, said it was a pity he had been gay, what a waste of a nice man...
And i came right out of my little closet:
"Well, mom, if he was a waste, i guess i am too..."
"But, but, but... Youre not a lesbian!!!!?" She said in horror.
"No, I am bisexual."
That is how I finally stopped saying, "well, i am straight but I know the kind of women i find attractive."
I have always been bisexual. At some point i became comfortable with it. Finally, I actually had words for who I am (remember when i grew up, 'homos' & 'dykes' were bad news - bi people were slutty and or confused and not trustworthy.)
I may never be involved with a woman again because I am married and monogamous. Were i to at some point marry a woman, i would be monogamous too. Casual sex isnt for me. Would this make me either straight or lesbian? No. I am who i am.
While i play with Willow's sexuality in fanfic - (and Xander, Giles and other people's sexuality), I believe CANON Willow is a lesbian
because she says so and because at no point does she show further interest in men.
She loved Oz, probably always will. They have a deep and real connection. Just like quite a few lesbians and gay men I have known who married the opposite sex for a variety of reasons having little to do with being straight.
Those whose spouses did not know before hand are often angry and justifiably feel lied to... Some forgive and stay friends, some don't. Those who always knew their spouse was gay or probably gay tend to be more accepting to begin with. There can be a lot of love there. Love is not neat or tidy. Neither is sexuality.
Btw, i have a theory why Willow did not date in high school. She did not act 'attracted' and boys did not see her as a potential partner. People reach out to people who they are attracted to AND those they think may be attracted to them too.
Oz was first attracted to her from a distance - because of who she seemed to be (a girl bold enough to wear an eskimo suit). He got to know her (career day) because of their shared intelligence. So he was not looking for the traditional cues...
After she cheated, Oz may have stayed because she knew he was a werewolf and that was uncomplicated. Until Veruca.
I think she may have been attracted to Xander because he was safe and Willow needed heterosexual self-validation... That attraction and dalliance does not make as much sense until after we know she is lesbian.
Yes, as a bisexual woman, part of me wishes she was bi. But that is not what i see.