I've been coming to better understand Buffy's character in light of how hard it is for her to connect to others (after all the tragedies and loss she's suffered over the years) and that she's basically locked up her heart and doesn't open it up to new people (she only says "I love you" to the Core and Dawn who was hardwired into her heart and mind). That her love is "blinding" and that's why she pulls away from it. It became harder and harder for her to say "I love you" starting in Season 5 and I think she's afraid of the tragedy and pain that comes from admitting that she loves someone, thereby loving them fully and openly leading to immense pain at losing them. She loved Angel in that way --- tragedy and pain. She loved her mom --- tragedy and pain. She loved Dawn that openly in Season 5 and Dawn constantly being in peril led to Buffy going into a catatonic state and even threatening to renounce her duties as slayer, even let the world end to protect Dawn. And arguably, her love for Dawn led to her giving up her own life in order to save her. Love that powerful is frightening and that's how Buffy loves - she loves "with all of [her] soul. It's brighter than the fire ... blinding. That's why you pull away from it." Her love overcomes her entire being.
I actually see Buffy referring to her love for Spike throughout Season 7 but just not being able to admit it openly because she has to deny her love or else she's opening herself to the pain of losing her loved one. "Love is pain" and Buffy continues to fear that pain.
Moments like "why does everyone think I'm still in love with Spike?" to her telling Angel Spike was "in [her] heart" - a vague euphemism that essentially means she loves him. The heart is emotionally symbolic of love - what other interpretation does this statement give us but that Buffy *does* love Spike but is afraid to admit it? Only when Spike is sacrificing his life does she find the courage to admit her feelings because 1) it's her last chance 2) Spike needs to know how she really feels and 3) his courageous sacrifice in turn inspires her to be brave.
Looking at the Spuffy story of Season 6 and 7, I see it as a tale of Buffy denying love or even the ability to love someone. Yet Spike continues to fight for her affection and in the end, she finally overcomes her fear to admit her feelings. The tragedy is that it's too little, too late. But it was real and it was a hard-won moment. I think the sad thing was that Spike didn't believe her in the end. She had protested so much that he finally came to the conclusion he wasn't worthy of her love. Their relationship was never easy, even to the very end. If that is the end.
I'll admit I think Spike didn't believe her when she said "I love you." I think the way he acts during AtS season 5 confirms that too. He even tells Angel that Buffy never loved him and that he doesn't think he has a chance with her.
I find their relationship always took the more difficult and complex route. The great romance moniker would more readily fit Buffy/Angel in a simplistic sense. With Buffy and Spike it's always felt more like an uphill battle against circumstances caused by each person's inner hangups. Buffy's fear of opening her heart to Spike, what loving him would say about her own inner darkness and the potential for pain afterwards. Spike's battle with his inner demon, his struggle to be worthy and his desire for love.
I find beautiful symmetry in Spike chasing Buffy for love and her running away, only to stop pursuing her when he gets a soul. Once he stops the chase, Buffy becomes the initiator of emotional support, no longer running but slowly building trust and the ability to declare herself. They're always chasing each other or avoiding each other. Fear and desire.
It's a wonderful follow-up to the Buffy/Angel tortured love story of loving each other so much but outside forces ultimately conspiring to keep them apart. With Buffy and Spike, it's their own inner hangups. When Buffy finally finds the courage to open her heart to him, it's now Spike who is too afraid, too guilty, feeling too unworthy to meet her.
It truly is a dance. A tango. Spike advances, Buffy retreats. Buffy advances, Spike retreats. It's part of why I feel their story hasn't ended where as Buffy/Angel feels like it's indefinitely on hold. Buffy/Spike feels more like an interlude before the dance begins again. But that's my hopeful side rearing its overly optimistic head. Or at least it feels that way in the fandom.