As others said already, it's quite a disturbing tale
The same as with Graham's though, I'm left with some questions, but I understand you may intentionally have left some things blurry.
Children
How many children *does* Annie's mother have?
Sissy, Annie, and "sisters and brothers" suggests at least 6.
What is the age span between the youngest, herself and Sissy? Annie is babysitting and knows about earning money, so I assume she is 15-ish; her "big sister" would be several years older, while children needing a babysitter would probably be 7 or under.
Jazz
"New Jazz, made by machines"
"Synthesizer"
It suggests that this record was created recently, as it is "new jazz", and Annie is listening to it for the first time after receiving it. Combined with the synthesizer remark, it makes me believe that the story is set in the mid-70's.
It also suggests that Annie knows the traditional jazz ("old jazz?") from the 20's and 30's. Why would a 15-year old girl, living in the seventies know 20's/30's jazz? Even Sissy maybe isn't old enough to have known it.
What does the Jazz stand for; old vs. new?
Do I understand the raven correctly, to be some sort of "bird of doom", appearing when Annie thinks about Sissy, the significance being that Sissy is actually evil in some way?
Whispering/tingling, the forest and "her people's past
I'm sorry to say I don't understand this bit... what people? Is Annie not human? What whispering? Does the forest portray being lost?