Belford sued her former husband, his parents and Gonzalez in 2009, claiming they worked together to carry out the kidnapping. She sought compensation for "medical, therapeutic, counseling, travel and other expenses."
Belford dropped the lawsuit in December 2011 after Thomas and Lenore Matusiewicz filed for bankruptcy protection in Texas.
"It became obvious that it was not going to be collectable," said Belford's attorney, James Woods. "I had no doubt she would win, and probably a very significant amount of money, for that torture they put her through."
Woods said the lawsuit was an attempt by Belford "just to try to get some justice."
"They had put her through hell, and it wasn't just David, it was certainly Lenore... and I found it incredibly hard to believe that Tom didn't know anything about it and participated in it, and Amy the sister as well."
Woods said that after Belford dropped the lawsuit, Thomas Matusiewicz sent him two thick packages of documents containing "all kinds of scandalous and ridiculous allegations" that Christine was abusing the children and was an unfit mother. The allegations were never substantiated, Belford was never charged and she was given full custody of the girls.
"It was obvious that there was so much venom they had directed toward Christine that it was almost palpable," Woods said.
Lenore Matusiewicz made similar allegations in a handwritten letter she addressed to Delaware Attorney General Beau Biden in January 2011. She was on probation at the time after serving more than a year in Delaware state prison for endangering the welfare of her three granddaughters related to the kidnapping.
She said her son was "paying the price for trying to protect his children...."
A federal judge who sentenced David Matusiewicz to prison noted that he never expressed any concern that his ex-wife was abusing their children until after he had been arrested.
A state judge who denied a motion by Lenore Matusiewicz to modify her prison sentence in 2010 also expressed skepticism about the abuse claims.
"Sadly, even if all the allegations of the defendant and her son are true, their decisions only seemed to harm the children more," the judge wrote.
Sherman contributed to the story from Edinburg, Texas.