An Alaska woman who arranged to have her best friend killed in 2019 after a man she met online promised her $9 million to do so was sentenced on Monday to 99 years in prison, state prosecutors said.

Judge Andrew Peterson of Anchorage Superior Court sentenced the woman, Denali Brehmer, 23, of Anchorage, who pleaded guilty last year to one count of first-degree murder in the death of the friend, Cynthia Hoffman, the Alaska Department of Law said in a statement.

Evidence presented at the sentencing showed that Ms. Hoffman, 19, was fatally shot on June 2, 2019, on a bank of the Eklutna River near Thunderbird Falls and that her body was later placed in the river, according to the Department of Law. Prosecutors later learned that Ms. Brehmer had been hired to kill Ms. Hoffman in exchange for millions of dollars.

During the hearing, Judge Peterson described the murder of Ms. Hoffman as “tragic and senseless,” the Department of Law said.

Patrick McKay, the Anchorage assistant district attorney, said in court on Monday that Ms. Brehmer “engaged in one of the most serious crimes that we have in Alaska.”

Ms. Brehmer had requested a sentence of 80 years with 20 years suspended, and prosecutors had requested a sentence of 99 years, the Department of Law said.