This preferance for white women therapists in this exact respect can actually be harmdul. because a white woman is not truly what she needs to talk to. also sarah has been looking for solace in a white people, she doesn't need an outside perspective, what she needs is someone who actually understands her.
this reaching for white people is what caused her confusion in the first place. Her desire for whiteness while being black- or rather her refusal to ackowledge the power/strength/beauty of her blackness is what kills her.
At once she states that she bludgeoned her father with a black mask/head. this is a metaphor that she was so hurt that her father chose the white life that she'd rather have him die as a black beast than to see him live as black man married to a white woman. so she killed him in an ugly portrayal of blackness- to justify her desire to be affiliated with white people. She doesn't want to claim her father or ackowledge her hypocrisy.
In fact, we can read her boyfriend as her therapist. he's white, jewish, and seems to find amusement in her lies, hatred, and body. this amusement of problems is because he's so far detached from the situation he can't provide any empathy and understanding to her actions and much less read into her obvious cries for help.
read more into the need for black ppl to see black therapists*