On Friday, police announced they've arrested 31-year-old David Goldsborough for killing her.
He is Leifheit's second cousin by marriage.
"The investigation has revealed that Goldsborough had developed an intense dislike of Destiny and her family which ended yesterday with tragic results," said Col. Rick Gregory, the chief of New Castle County Police.
On Thursday, school was closed for staff development and Destiny was home alone. It appears she let Goldsborough in, and was attacked.
She was found with multiple stab wounds on most of her body by her great aunt, who is also Destiny's guardian.
Goldsborough's mom maintains he would not hurt a fly.
"He would endanger himself before he would endanger anybody," said Mary McCready. "If the cops came up and said David was a suicide, we would all believe that. But him going around and doing something to somebody else? No."
"He was found at home and was intoxicated," said Col. Gregory. "He had deep cuts to one of his left fingers as if he'd been in a struggle."
Police found a 12 inch sword, thought to be the murder weapon, among a collection of Goldsborough's knives, in the home he shares with his mom, her husband who is also Destiny's great uncle, and Destiny's little brother Christian. They live a few doors away from Destiny's home in Hunter's Glen trailer park.
"We're all having a very rough time right now and a 13-year-old girl should have never been killed," McCready said. "She's related to us and we all love her, and whoever did it should pay the price."
David Goldsborough has been charged with murder and animal cruelty after Destiny's chihuahua was also found stabbed to death inside the trailer home.
Action News has been told Destiny's mother, who lives in Tennessee, will be coming to Delaware.