CHICAGO (CBS) — Eight years ago this week, Stacy Peterson disappeared from her home in Bolingbrook.

As her husband, former Bolingbrook police officer Drew Peterson, sat in prison for the murder of his previous wife, Kathleen Savio, Stacy’s sister marked another anniversary and said she’ll never give up the search.

Cassandra Cales was one of the last people to see her sister, Stacy, who wanted out of her marriage to Drew when she vanished. Cales said, after eight years, it doesn’t get any easier.

“It’s still a rough emotional roller coaster ride, and I just take each day and work through it, and there’s not a day that I don’t think about her, and I just stay positive, and cherish the memories we had,” Cales said.

Cassandra Cales' sister, Stacy Peterson, disappeared in 2007. She believes her sister's husband, Drew Peterson killed Stacy. He hasn't been charged in that case, but is charged with killing his previous wife, Kathleen Savio. (Credit: CBS)

Cassandra Cales’ sister, Stacy Peterson, disappeared in 2007. She believes her sister’s husband, Drew Peterson killed Stacy. He hasn’t been charged in that case, but is charged with killing his previous wife, Kathleen Savio. (Credit: CBS)

She said she believes her sister is buried close to the home she shared with Drew Peterson.

“I wish he’d give it up already, you know? To give me and my family closure. We’re not really ever going to have closure, but it gives her the proper burial, and then we can have a proper funeral, or service, or something, and then kind of try and put it behind us.”

Cales said she takes some comfort in knowing the man suspected in Stacy’s disappearance is in prison, even if he was never charged in connection with Stacy’s disappearance.

She makes the 300 mile trip to downstate Chester for his court appearances on charges he tried have prosecutor who put him in prison, Will County State’s Attorney Jim Glasgow, killed.

“I like to go see him, and how miserable he is, and he won’t even look at me. He looks pretty unhealthy, and I don’t think he’s going to last much longer in there,” Cales said.

She also said she’s still out searching for her sister’s grave.

“I’m never going to give up. I’m always going to keep searching, and checking places that I feel, or any little tip; whether it’s a psychic, or some crystal ball lady saying she could be over here. I’ll still go check it out,” she said.

This week, as another anniversary of her sister’s disappearance came, she was plotting the next areas where she would go and search for her sister’s grave. She estimated she has probably searched hundreds of times over the years.