I don't know how anyone can think she didn't love Spike.
My brain is all fuzzy and tired right now, so I really don't have the brain power to analyze Buffy on more than a Giles = hot level, so intelligent analysis and critical insight will have to wait for another day. The gist of my usual argument, though, is that I think that of all of Buffy's romantic relationships, Spike was the person with whom she had the deepest, most meaningful connection. They began as worthy opponents, then they became reluctant allies, then friends, then lovers, and then, finally, they fell in love. They knew each other on all levels. They knew each other's strengths and each other's weaknesses. They'd seen the best AND the worst in one another. Over the course of those experiences, they forged a connection. Spike knows Buffy like no one else does. And she knows him like no one else. That kind of love isn't pretty. It's not hearts and flowers and its not for kiddies. But it's real and it's lasting and it'll get you through an apocalypse or two -- literal or metaphorical.
In many ways, their relationship reminds me of the one that I have with my hubby. No - we never tried to kill/rape/maim or otherwise harm each other. I'm just saying that we've known each other since we were kids. We've seen each other through crises. We've seen each other with other partners. We've seen a lot of not-so-stellar moments (okay; most of those were mine). Other men tried to put me on a pedestal. They wanted to love their perfect idea of me and ignore or deny the rest. But my hubby... he loves me warts and all. He can acknowledge my faults and love me not in spite of them, but even in part because of them. And I feel the same way about him. I, personally, am hard-pressed to call any other kind of love "love."
So when someone asks me whether or not Buffy loved Spike, I always think, "how could she not?" You don't bare your soul - warts and all - to someone the way she did with Spike and walk away with your heart untouched. She let him in in a way in which she has never let anyone else in before or since. I'm not saying he was the love to end all loves or better than or worse than certain other loves. I'm just saying that if what I saw develop with them over time and come to fruition at the end of season 7 wasn't love, then I don't know what is.