Maybe that's why she hates him so much. Seething rage chokes her even as his cock is buried deep inside of her. The lust in his eyes she can take, but his pathetic adoration makes her want to grind him into dust.
He's evil and he's weak.
Buffy despises things that are weak, including herself. Hates how she is too weak to fully pull herself out of her grave. Hates how insignificant things like making breakfast or folding laundry exhaust her soul.
Hates how just thinking about his touch makes her wet. Hates how her knees turn to jelly when his hand slides between her thighs and wanders upwards. Hates hearing herself gasp when his tongue laps at her clit while his expert fingers thrust into her. Buffy hates.
He talks all the time, calls her amazing, his ferocious wildcat, tells her how he loves the taste of her cunt, mixes poetry and profanity - too many words. In the end she rides him, screeching like a cat in heat, using all her strength and fierceness to reduce him to grunts and moans, to make him shut the fuck up.
Afterwards, when he gazes at her with awe, she grabs her clothes and rushes off. She knows she'll be back.
Spike never bites her, but maybe someday he will.