After she came out during the fourth season, the fandom quietly decided that Willow had a huge crush on Giles' girlfriend Jenny during the second season. It's one of those things that just makes sense, what with Jenny inspiring Willow to start dabble in magic, the thing that later would become a not-so-subtle metaphor for lesbian sex. It is also canon that Willow has called Jenny her favorite teacher during that time frame. Given that Jenny was the computer teacher, she may have also inadvertently helped initiate Willow's hacking abilities too. Whether she had/has similar feelings for Buffy is debatable.
- S8 makes it a little less debatable since Willow grills Satsu on what Buffy's like in bed (including how she sounds when she orgasms). Then she denies ever having a crush on Buffy to Buffy after telling Buffy to be careful with Satsu. Buffy in turn, almost petulantly, denies having a crush on Willow because Willow denied to Buffy first. Later on, in another issue, Kennedy starts showing jealousy telling Buffy, "But you put the moves on Red and I'll kill you like a chicken."
Willow: And just so you know... I never wanted to sleep with you either.
Buffy: What are you talking about?
Willow: I'm sayin' it's a good thing you didn't try your little experiment on me. 'Cause it wouldn't have worked, Summers. You're not even on my list.
Buffy: What list? There's a list?
Willow: Yep. And you're not on it. Not my type.
Buffy: Oh, yeah? Well, then, you're not on my list either!
Willow: Good. I don't want to be.
Willow: Eww. Just got the visual.
Buffy: And other people too. Those are just examples off the top of my head.
- Then there's season 9 which opens with Buffy after a night of drinking and partying, thinking she did the naughty with Willow and her very heavily suggesting they did. This was after asking if her married ex had porn then tried hitting on him. This was right at the time Andrew brought back the Buffybot and put Buffy's mind into it in a bid to lure out the Big Bad, so not only can her behavior be excused on account of being wonky, if Willow was serious about sleeping with Buffy then she did it with the bot, not the Slayer, kinda.