How we cite our quotes: (Chapter.Paragraph)
Quote #7
She dreamed of her old adversary, Trembling Sally, the nuisance who stalked her slumber. Trembling Sally was a troubling woman in the rapids of her dreams, a drunken tempest raging in her inner ear, one who wailed an awful wailing. Her sound scalded peace. (29.17)
Okay, so we know Trembling Sally's lost her mind—but here we see how mentally unsettling she is to Abyssinia, too. She "scald[s] peace" inside Abby's brain, wreaking havoc on this otherwise totally sane character.
Quote #8
The wild woman let out another tortured wail and, wielding her flaming torch, rushed toward the fleeing Abby. (29.33)
Part of what marks Trembling Sally as insane in this text is the idea that she's "wild"—she doesn't play by society's rules or share their investments, instead following unpredictable whims and doing things like, say, trying to murder four people in their sleep for no apparent reason.
Quote #9
The crazy, hollowed eyes of the woman stared at the free Abby. Then her torch lit the bedroom curtains. Fire danced on the bed, burning the crazy patch quilt, the feather mattress, and the feather pillows. But the fire was not satisfied.
Now the wicked fire demanded more. Its violent, ruby mouth kissed Sally. Sparks leaped up her clothes and sizzled.
The crimson flame licked at the pitiful woman, turning her hair to black straw. (29.36-38)
Ultimately, Trembling Sally succumbs to her own madness, destroyed by the fire she sets in an(other) attempt to kill Abyssinia. Note that Sally's described as "pitiful" here—she's a victim of herself now instead of a menacing terror to Abby. The fire "demands" to consume her, overcoming her with its power the way she's so longed to overcome Abby with her own.