What Ana is referring to is that Joss wanted for Buffy to have as intense a relationship as she did with Angel, but not a boyfriend-girlfriend relationship, so Joss brought Dawn in as Buffy's love interest in S5. If you want a quote from Joss, No Angel, I can get it for you. I don't think Spike is Angel's replacement because first of all, Joss wasn't aiming for that after Angel left. Spike doesn't have the same ambitions after he got his soul, nor could Buffy *truly* love him, IMO.
Angel and Bufffy are doomed basically until Angel becomes human, so I don't thinki they would've even stayed together much longer...