RAPID CITY, S.D. (AP) – A longtime advocate for Native Americans, Thelma Rios saw her good works overshadowed by her involvement in the 1975 slaying of another American Indian Movement activist.

Rios' attorney Matt Kinney said she was diagnosed with lung cancer shortly after he negotiated a plea deal for her in the woman's death. She pleaded guilty as an accessory to kidnapping in November. The office of another of Rios' attorneys, Randy Connelly, told The Associated Press she died Feb. 9 at a Rapid City Hospital. She was 65.

Connelly told the Rapid City Journal her death was a “sad day” for the Indian people on whose behalf she often worked.

“She was a warrior. There was no greater warrior for her people and her fellow man than Thelma. She assisted her people in many, many ways,” said Connelly, who had known Rios since the 1970s.

Rios was convicted for her role in the death of Annie Mae Aquash. She admitted in court last fall that she relayed a message to other AIM members to bring Aquash from Denver to Rapid City in December 1975, because they thought she was a government informant. Investigators have denied Aquash was a snitch. Rios also said she opened up her apartment so Aquash could be interrogated.

Aquash was later found shot to death on the Pine Ridge Indian Reservation. Two men have been convicted of murder in her death.

Rios was sentenced to five years in prison, but a judge suspended the sentence and ordered her to serve five years of probation.

Attorney General Marty Jackley extended his condolences to Rios' family and said he didn't expect her death to interfere with the filing of future charges in the Aquash case.

“While I do not condone the criminal venture that kidnapped and executed a young mother, it is important to recognize Ms. Rios' acceptance of responsibility for her involvement and her willingness through the plea agreement to provide assistance to authorities,” he said in an e-mail to the Journal. “The prosecution has overcome many evidentiary challenges stemming from this 35-year murder case, and while this certainly may give rise to future evidentiary issues, I do not anticipate it will have an overall effect on holding those involved in this brutal murder responsible for their actions.”

AIM was founded in 1968 to protest the U.S. government's treatment of Indians and to demand that the government honor its treaties with tribes. The group took over the village of Wounded Knee on the Pine Ridge Indian Reservation in 1973, leading to a 71-day standoff with federal agents.

Connelly said Rios' conviction in the Aquash case cast an unfair shadow over her life, which he described as “filled with character and integrity.”

“It puts an improper and unfortunate punctuation to the end of her life. It truly, truly does,” he said. “Her involvement, I've always believed, was totally unwitting in a sense.”