Genene Jones, 62, is scheduled to be released from prison in February 2018 under the state's mandatory release guidelines.
Jones was found guilty of murder in 1984 and sentenced to 99 years in prison.
Recommended Videos
She was convicted of injecting 15-month-old Chelsea McLellan with a lethal dose of the powerful muscle relaxant succinylcholine.
McLellan's mother had taken the child to a Kerrville clinic where Jones worked.
"Texas is going to release a serial killer of children," said Petti McLellan-Wiese, Chelsea's mother.
San Antonio attorney C.N. "Nick" Rothe, who served as special prosecutor at Jones trial, was outraged at Jones proposed release.
"I don't see that she is the kind of person that the system ought to let go at any point in time," Rothe said. "The person who does that has a deficiency as such that cannot be overcome by any good deeds after that."
Good behavior during her prison stay has earned Jones time off her 99-year sentence.
"The best place for somebody like that is to stay in the hole where they are," Rothe said.
McLellan-Wiese recalled how her daughter died en route to a San Antonio hospital from the Kerrville clinic after Jones administered a second shot of succinylcholine in the ambulance.
"I said, 'Something's wrong, something's wrong,' and she was like, 'No, she's just mad because she's gotten a shot,'" McLellan recalled.
She said that was after the first shot, when little Chelsea began having breathing difficulties.
A lengthy investigation by authorities in San Antonio and Kerrville later validated McLellan-Wiese's suspicions.
Jones was indicted for murder in McLellan's death.
She was also a suspect in over 40 suspicious baby deaths in San Antonio and convicted of attempted murder in one case.
News of Jones' impending release shocked McLellan's mother.
"It has never been over and now it's really not going to be over," she said.
To help alleviate over-crowding in Texas prisons, inmates are allowed to accrue "good time" for good behavior.
Lawmakers banned the practice in the '90s for violent offenders but the United States Supreme Court ruled that the state could not apply the change in the law to cases prior to 1987.
For a list of recent stories Paul Venema has done, click here.