Sandra Reyna has been behind bars since the death of her 2-year-old son, Austin Contreras, two years ago this month.
She's now serving a 20 year sentence as part of plea deal on a lesser charge from murder.
Debbie Brennan is fighting to get her daughter out of prison.
"She should get another court hearing," Debbie said. "She should be able to have that opportunity of proving her innocence... Due to the fact that they did not have any evidence at all."
A lack of evidence is what led to a murder charge dismissed this week against Sandra's ex-boyfriend, Adan Acuna.
Debbie is shocked to learn how the only person alone with her grandson, just before he died, is now free.
"He was with my grandson... He was responsible to take care of my grandson... Boyfriend or not... He was still considered a babysitter," she said.
An autopsy shows the boy died from blunt force abdominal trauma.
The Hidalgo County district attorney says Acuna did not inflict the injuries causing Austin's death.
Sandra, however, already had a number of abuse cases against her with child protective services, according to the district attorney
The mother of five, inked a deal with prosecutors for an injury to a child charge last year, to avoid a possible maximum sentence of 99 years for murder.
Debbie blames her daughter's court-appointed attorney and the state for a "coerced" agreement.
"The attorney had thrown the pen on the table and yelled at her and said 'sign it'... He said '20 or 99 years... What do you want'... when you're looking at life... Your choice would be to sign 20 years... You're not in your right mind... You're just thinking life... You're fearing for your life there and not seeing your children forever," she said.
Sandra's court-appointed attorney did not return a late evening phone call for a comment.
Meanwhile, her mother's case for an appeal is highly unlikely to happen.
The district attorney says Sandra TMs plea deal last year stipulates no right to appeal.