In a taped interview that aired Thursday on Dr. Phil, Diena Thompson talked about how she's trying to stay strong in the wake of the tragic death of her daughter Somer last month and how she's on a quest to find her daughter's killer.

Diena appeared on the show as part of a discussion about abductions. Somer went missing while she was walking home from school, and her body was found days later in a Georgia landfill.

"I feel like Somer's pushing me," Diena told Channel 4's Laura Mazzeo Thursday. "She's keeping me with my eyes focused to what needs to happen."

Diena wears her daughter's picture around her neck every day. She dresses in purple, Somer's favorite color. And with each day that passes, she says investigators restore her faith.

"I think their attitude is even more positive than mine," Diena said. "They've assured me that they're not and that they are moving forward in positive strides, and that they have every intention of never letting this case get cold. Most of them told me they wont retire until this case is cold."

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Sheriff Rick Beseler answered questions Thursday about what evidence has been found three weeks into the investigation.

Beseler said some forensic evidence is back from the lab, but he won't say what it is.

Beseler did not release any information on whether investigators have tracked down the Dumpster where Somer's body was originally placed.

As for the home on Gano Avenue that investigators searched, Beseler would not say if the crime took place there, but he did say it has not been ruled out.

Investigators said they are using a high-tech computer system that analyzes the Internet for anyone boasting about the crime. They have received more than 3,600 tips in the case.

Diena said she believes with so many resources and agencies still in on the case that justice is coming soon.

"He can't be smarter than the rest of is," Diena said. "It can't be smarter than the rest of us. There's nothing a 7-year-old could do to deserve what she's been put through even though I don't know what that is, but I have my own story in my mind. As I've said before, I don't know if it's more gruesome than what's actually happened, but when you're left to your mind, it can show you some horrible things."

Police still aren't releasing information about how Somer was killed, and Diena said she needs answers.

"I really want to know why, why," she said. "I want a big T-shirt with a question mark why, but I might not ever get this answer because this person probably absolutely has no reason, just pure evil."

Diena said she is passing the days trying to focus on her three other children.

"I'm still a mess," she said. "I can't have my eyes off of them."

She said every night her children ask her to sing "You Are My Sunshine."

"It's hard to sing them her song, but if that's what makes them feel better then that's what I've got to do," Diena said.

If you know anything that could help police in their search for Somer's killer, you're asked to call the Clay County tipline at 877-227-6911 or Crimestoppers at 866-845-TIPS. You can also e-mail Clay County investigators at cart@claysheriff.com. The total amount of reward money in the case stands at $45,000.