"The policemen, the detective, they told us not to say nothing to Melissa," she said. "I don't know. They said that they talked to Melissa, but I don't think they did. Because if they talked to Melissa, then something else would have been done."
The teenager also claims the family filed a police report, despite police insistence to the contrary.
Because all reports filed in connection with the brief disappearance of the 7-year-old are now part of the Cantu investigation that will be used to prosecture Huckaby, Sheneman said he could not share any details of what police had learned.
The young woman said her sister had been treated well previously when she had been with Huckaby, playing with her daughter. And she had never seen her act inappropriately with children before that day. But after her sister returned home on Jan. 17, the woman said she was never allowed to be with Huckaby again.
The girl's family said they were surprised to learn that Huckaby had been arrested in Sandra's murder because they, like many others, including the police, had expected the suspect to be a man. But still, she said, "there was some suspicion in my house after what happened to my sister."
The teenager said her family is confident police arrested the right person for Sandra's murder.
"It's sickening," she said. "How you can do that to somebody so young, and so innocent for no reason?"
This is the latest twist in the case against Huckaby, 28.
Just days after 8-year-old Sandra Cantu was laid to rest, a court is slated to hold a hearing on the request to exhume the second-grader's body.
Sandra'sprivate funeral was held last Wednesday. One day later the request was filed to exhume her body so the defense for accused killer Melissa Huckaby would have an opportunity to conduct its own autopsy.
Huckaby's attorney, Deputy Public Defender Samuel Behar, professed to have no knowledge of the case when contacted by ABCNews.com, but a court document filed by Behar Thursday indicated the request was based on the deputy district attorney's belief that Sandra had suffered "genital trauma consistent with forcible penetration."
In the court document, Behar said the defense needed to examine the alleged trauma so Huckaby would be able to defend herself. He also requested the exhumation take place quickly, alleging that deterioration would cause Sandra's body to have "progressively diminishing value."
A San Joaquin Superior Court spokeswoman said a hearing on the exhumation request is scheduled for Friday, the same day Huckaby is due back in court for a further arraignment where she would have the opportunity to enter a plea.
San Joaquin Deputy District Attorney Robert Himelblau told ABCNews.com Monday that his office would be filing a response to the request but did not elaborate.
"I wish I could, but I can't," Cantu's aunt, Angie Chavez, told ABCNews.com Monday.
Chavez said the family was mostly holding up as best they could. They were shocked at the massive turnout for Sandra's public memorial service, held Thursday.
"We were very surprised," Chavez said. "We knew she touched a lot of people."