The cycle of violence, retribution and attempts at justice transfixed Long Island for years.

On Sept. 14, 2016, the body of Kayla Cuevas was found, bludgeoned to death by members of MS-13 and left beside a house at 6 Ray Court in Brentwood.

Two years later exactly, her mother, Evelyn Rodriguez, who had become a renowned anti-gang activist, was run down on Ray Court by the homeowner’s daughter. The daughter, Annmarie Drago, had grown weary of unceasing memorials near the property, prosecutors said.

The prosecution of Ms. Drago followed a byzantine nearly six-year path of conviction, reversal and retrial as attention seeped away and Ms. Rodriguez’s family fell to pieces. On Tuesday, the case appears set to end in a Suffolk County courtroom, with Ms. Drago, 63, likely to receive no more jail time than the one week she already has served.

For Kelsey Cuevas, 26, Kayla’s sister and the sole survivor of a tight triad of women, it has been a torturous ordeal with an unjust ending.

She has struggled to reassemble her life while raising two young children who will grow up without their aunt or grandmother. She lives on Long Island but refuses to say where, terrified that the gang will come after her. On some days, she still picks up the phone to call her mother, forgetting that she’s gone.

“Being diagnosed with PTSD, I just feel like there’s a part of me that’s like just really loose,” she said on a recent morning, taking a long drag from a spliff as she spoke.