I'm sure this'll turn out to be a long post, but then again, Buffy's relationships are never as easy as a sentence or two for me.
😉
There is a lot of tension between Faith and Buffy that's very complex. But then, I can't recall any relationship that Buffy's had that's not been hopelessly tangled and confused at more than one point where love (whether of a friend or a lover) was involved.
Faith does want Buffy to love her, has always wanted that - which the Mayor painfully pointed out in Season 7 - but she's completely the opposite of Buffy. Where Buffy thinks, Faith acts. Faith's much more about anger and action, and Buffy is someone who wants to understand and communicate. So instantly, they click on some levels, and repel each other, on more fundamental levels. Faith is Buffy's opposite, but Faith is attracted to the light and warmth that Buffy and her friends and family have together. In many ways, she does want to be let in and she does want to be loved and accepted and to be close to Buffy, and leave behind the old, damaged Faith. When Buffy rejects her, and Faith starts to feel like she's not doing anything that makes her happy, she just continues to screw things up and that drives a wedge in between them that's still there today.
I've
always thought that they were interested in each other. But being interested does not a relationship make. They were definitely feeling each other out, but I think a lot of that was because: here's this other Slayer, when I thought I was alone in the world. Being able to sense each other on some level, and experience the same feelings and dreams, must have been something they wanted to explore. Getting that close to someone, especially at a time when you might be working through some things or feeling alone, other feelings might pop in there completely unexpected.
The vibe I got from Faith is that she just didn't know how to express her feelings about anything, much less about wanting people to love her, especially of needing Buffy's approval and love (Faith is like a bull in a china shop about things sometimes). She saw that as a weak point in her armor, and so she rejected that need and overreacted to compensate and lost control, and just took Buffy to the edge as she was going over, herself.
I feel like Buffy picked up on that, all of it, because she's a smart girl. Her mama didn't raise no fool. She has a 6th sense about a lot of things, and she's extremely empathetic to people, even moreso to those who she's close to. She understands a lot about emotions, sacrifice, and love, even in Season 3. But obviously, at this point in time, there were more important things happening in her arc with Faith besides finding time to sit down and talk about feelings.
Season 7 and Season 8 would still see their relationship changing, but still bouncing back and forth between the old angst and anger. Almost the whole way they relate to each other now is colored by their history together. They go around and around on the same track. I'm not sure they're ever supposed to be able to get past that.
To sum up, I think there was a lot of attraction and curiosity there, and Eliza and Sarah played it like that on purpose. The subtext is there and it's intentional. The hint that there was something beneath the surface with them was not really going to go anywhere, though. Is it going anywhere now? No clue, whatsoever. All I do know for certain is that everybody important - Joss, Sarah, Eliza, & main Faith writers - knows that there's static and spark between Faith and Buffy, and I think they enjoy tinkering with that and giving it a little nudge now and then to see what happens.
Doug Petrie said in the commentary for
Bad Girls:
"And here we’ve got the growing lesbian subtext between these two, which was always fun to play with. And Eliza was always kinda pushing the sexuality and no one remembered to stop her from doing that, which we’re all very happy about."