I’ve already discussed Buffy’s decision not to tell the Scoobies about her mistreatment of Spike here. This is more general about Buffy’s behavior in early S7.
*Warning for discussion of rape and abuse*
First of all, can we take a moment when discussing Buffy’s early S7 attitude towards Spike to remember that Spike tried to rape Buffy?
Second, I think the vampire who even with the soul loves making comments about all the people he killed, as if there’s nothing wrong with that, can handle his ex making a few stupid jokes.
Third, Buffy is not a mental health professional. Tragically, there are no mental health professionals for vampires (I wish the guy from CWDP had gotten a chance to analyze his sire…). We saw what happened in S6 when Spike, who was not a mental health professional, tried to help Buffy with her depression. It was a nightmare. Now, obviously, Buffy is not a soulless stalker-vampire, but given her history with Spike and the abuse on both sides, I can understand why she might want to keep her distance (until after she gets in her own therapy season in CWDP).
Fourth, yes, Buffy should have gotten Spike out of the school basement sooner (although she didn’t take as long about it as it seemed). But where? Having him come stay with her would have been a bad idea at that point for multiple reasons. That leaves Xander. Xander, who tried to kill Spike shortly before the vampire left town, just because Spike slept with Anya. This after having fought beside Spike time and time again, and after letting Spike watch his best friend’s little sister. It’s noteworthy that Buffy waits until *after* Xander learns what it’s like to have your best friend try to kill your demon ex before she asks him to take Spike in.
I actually have more sympathy for Buffy in “Help” than Spike. If the guy who tried to rape me went on and on about how guilty he felt about what he did to me, and then asked me to stay, I don’t think I would be polite, either, mental illness or no.
And from at least “Same Time, Same Place” onward, Anya, Willow, Xander, and probably Dawn all knew that Spike was crazy in the basement. I didn’t see any of them trying to help him.
As I may have said before, I also think Buffy avoided Spike in part because she was afraid that he might hurt her, or she might hurt him. She trusted neither him nor herself. She didn’t know if souled Spike would try to rape anyone. Unlike the viewers, she doesn’t know that Spike wasn’t violent as a human (in fact, it’s implied in Fool for Love that Spike told her just the opposite). Buffy doesn’t know what it means for a vampire to have a soul. She’s in denial about vampires, and their capacity for love, and souls, and the humanity of the creatures of the night.
Also, in some ways, I think she was angrier at Spike about getting a soul for her than for trying to rape her. But she isn’t allowed to be angry about the former, because that isn’t something she has a right to be angry about. But I think it makes dealing with Spike difficult.
I wonder if she feels at all guilty about the fact that Spike got a soul for her?
I also wonder if there was some left-over resentment from his inability to help her in S6. Again, it wasn’t his fault, and it wouldn’t be a rational reaction for Buffy to have, but to have him show up with a mental illness after he had let her down (And she really did trust him in S6. She really believed in him.), would be hard for her. And I think part of the reason she avoided him is because she knew she might take out her resentment on him, and he didn’t deserve that. Not from her, anyway.
In conclusion, I think there are a lot of reasons why Buffy behaved the way she did. I think the point of the trigger was to show us that Buffy keeping her distance was a mistake, but given the nature of her relationship with Spike, it would be hard for her to do otherwise.