JACKSONVILLE, Fla. -

A 55-year-old Jacksonville woman was sentenced Thursday to 50 years in prison after pleading no contest to second-degree murder in the killing of her 24-year-old daughter in December 2011.

Silvana Catignani was facing a life sentence. She also pleaded no contest last month to possession of controlled substances with intent to distribute, prescription drug fraud, and tampering with evidence.

No one in Catignani's family spoke on her behalf at Thursday's sentencing. A judge asked several times if she wanted to say anything, and her only response was, "I didn't do it."

Police said Catignani and her daughter, Nicole Catignani, got involved in an argument, and they said Silvana shot Nicole once in the head through a pillow.

Detectives said instead of calling 911, Silvana left the house to get rid of the gun.

Police said inconsistencies in her story and cellphone records led to her arrest. They said the records revealed she wasn't where she claimed to be.

Police said Silvana told them she threw away her pistol two months before the shooting, but two people told police they saw her with the gun the night before.

"I felt relief. I know she's 55 now, so by the time she gets out, she won't get out," said Ashley Corley, Nicole's best friend. "So I'm just really glad that justice is being served for my best friend today."

Police said the mother and daughter were running a pill operation out of their Mandarin home.

As Judge Suzanne Bass read the sentence, she told Catignani that her daughter couldn't defend herself the night of her death. Detectives said she was under the influence of drugs when it happened, and Catignani knew it.

Bass also mentioned the fact that the mother got rid of the gun off the Buckman Bridge, had a friend call police, and denied responsibility.

Despite the issues Nicole faced, her friends say she didn't deserve to die like this.

"She had a heart of gold," friend Crystal Register said. "Every time my little sister was in the hospital -- she passed away in February -- Nicole was there right beside her. If you needed something, she'd give you the shirt off her back."