drew having bpd makes a lot of sense to me, btw. it's the way that silena was her favorite person whom she idealized to such an unhealthy degree, that the consequent "betrayal" completely incapacitated her and ultimately led to "splitting". in bpd talk, splitting is when someone who suffers from bpd becomes entirely disillusioned by a person they once held in high regard ( their fp or favorite person. ) splitting is basically some sort of polarized, black and white mentality: one moment, their fp is the sun and stars, the next they are the worst ever, because of the betrayal / the abandonment, perceived or otherwise.
it is ultimately the reason why drew cannot forgive silena as easily as the others were able to. while they could justify silena's actions as heroic bc of the strain she was under + the choice she made in the end, to drew, none of those things mattered. there is only her trust, her admiration, her shining love, and how all that was broken. and in true bpd fashion, she had a hard time managing her emotions, and all that anger overflowed onto other people. it's very important to note that drew is young and immature, and doesn't have all the tools yet to manage her symptoms. she is not yet aware that she needs help.
i have more on this, but i also think that there are notable changes in drew before and after silena's death. one of the key features of bpd is an illogical fear of abandonment, along with inappropriate and intense anger + difficulty managing impulses and wild mood swings. drew's unfortunate treatment of her siblings echo all this: she's angry and lashing out. she's keeping them at all arm's length, employing a preventative measure in terms of fostering any possible closeness, because she's afraid they might abandon her eventually, so she might as well get a head start by removing any good will whatsoever. to drew, it is easier to make them hate her than to have them be close to her, if they were going to leave her at some point . fresh from the trauma of losing silena, this is how drew preferred to protect herself.
now, i will say again what i have always said: in no way does this make her actions correct. she's had a lot of failings, and her mental illness does not exclude her from being held accountable for how she treated others. but i do think it puts things in perspective, when thinking of her character + her actions in HOO canon.