the other thing about the episode darla is that it’s part of a matched set with the btvs episode fool for love. many of the flashbacks are the same across both episodes, just cut to focus on different pairs (darla/angel in angel, drusilla/spike in btvs) within the sort of vampire polycule thing. so because of that, it makes sense to look at them as thematically linked. both episodes deal with what it means for a vampire to love someone. darla and drusilla create angel and spike respectively and both abandon them because something happens to change them. both angel and spike desperately want their creator/motherwife to take them back. neither gets what they want. both, in the present day,
part of what’s interesting though is that they end very differently. angel keeps trying to help darla in the hopes that she’ll reciprocate his love, only to realize she sees their relationship as transactional. spike seems like he’s going to have a similarly frustrated ending: he’s unable to convince buffy of the connection he feels they have and, hurt by her statement that he’s beneath her and that she’d choose someone else to kill her, decides to kill her for good (with a shotgun, one of the few times in the series a character opts to use a gun). however, when he gets to her, she’s crying about her mother’s health problems and he finds himself unable to go through with it and opts to try to comfort her instead. it’s an awkward moment (he’s inexperienced and she’s unnerved) but unlike angel he’s able to change who they are to each other. it’s small and clearly feels weird to both of them but it marks a huge shift.
so then you kind of have the question of why is spike able to end the episode connecting with someone he loves (and in the process changing how he loves) while angel (the hero) isn’t. there’s a couple differences between them but I think a lot of it comes down to a willingness to adapt. angel is still trying to pursue darla and he’s not really willing to change how he does it either. they each need each other to be a specific thing and neither of them will bend. spike, however, is more willing to give up. there’s a sort of misogynist-violence aspect to the way he gives up initially (she rejects him and he feels humiliated so he has to annihilate her) but still, it’s only by giving up on her being to him what he wants her to be that he’s able to try something else: treating her like a person who is going through something.
angel and darla don’t really treat each other as people. for darla, angel is her soulmate, her handiwork, and someone who owes her a favor. for angel, darla is himself mirrored, a prolific vampire who now has a soul and is going to go through exactly what he went through. it doesn’t to him that she might experience this differently. it doesn’t occur to her that ensouled!angel is as real as angelus was. spike initially has a similar failure. he sees buffy as the slayer. her gift is the same as his (death). his “lessons” are pure projection. he thinks the slayers he killed were asking for it (more subtextual misogyny) partly because he himself is (the desire to fight the slayer to the death is equally about the possibility of her killing him). but, at the last moment, he’s able to see her as a person. she’s not the slayer, she’s buffy, someone he’s known for years, and she’s crying on her porch because her mom is going through medical problems she doesn’t understand and can’t fix. and spike might not really know how to help either but he knows that he doesn’t know and he’s willing to try to figure out what she specifically needs.
it’s a shift that i think is narratively interesting for a vampire character, especially an antagonist with a history of onscreen misogyny and abuse (case in point his relationship with harmony). in order for him to stick around, and for his relationship to the other characters to start to change, he has to start seeing buffy specifically (but other characters as well) as people. part of that is a change in how he treats women (since they are the majority of the main cast). we saw him commiserating with anya in season 4 and from here on we see him developing friendships or at least rapport with the entire summers family. he’s still often creepy or stalkery but you see him trying to be a friend to both dawn and joyce for example.
it’s also a shift that i think that is allowed partly by the fiction of the show. spike is a vampire, which sets the viewers’ standards for his behavior very low. any improvement is cause for celebration because his instincts are constantly pushing him towards predation and violence.
