I have a great WIP where Buffy doesn't fall first but once Spike loses interest she changes her mind and, in a completely non-spell induced way, pines for him and really tries to get him to change his mind but he could not be less interested. It's a natural progression, it's just that it happens after Buffy rejects Spike for a period of time.
Irony Becomes Her by starmousehttp://www.fanfiction.net/s/916876/1/Irony_Becomes_HerAnd there is a brilliant post-Chosen fic where Buffy finds Spike 'resurrected' so to speak and living his new human life without her and he is completely uninterested in her but she perseveres because she knows what she wants now. It's a great story:
My Life Closed Twice by anarosshttp://www.athenewolfe.com/justrewards/viewstory.php?sid=577There are of course many all human fics with these parameters, but since you are asking for recs I assume that you are not seeking all human ones. The canon ones are much rarer.