The emaciated remains of the two girls were found in a shallow grave where the couple and children were living with Butler's parents in Hepburn Township, Pa.
Echo Butler's parents, Ronald and Michele Butler, lived with the two women and authorities charged them with helping to starve the children then assisting them with covering up the evidence of the abuse and deaths.
"They were being starved and beaten every day," the girls' mother admitted while on the stand. She's been charged with criminal homicide along with Echo Butler.
"Echo would grab their throats so they couldn't breathe and choke them until their eyes would roll back into their heads," Snyder said.
The girls' bodies were found after an investigation began into concerns of Snyder's 7-year-old son not attending school, according to court documents reported by local TV station WOLF. Lycoming County Children and Youth Services visited Snyder's home when they discovered the two girls, Nicole Elisabeth and Jasmine Jean Snyder, were missing.
After child welfare workers couldn't locate the girls -- who were supposed to be 11 and 8, respectively -- police were called to search the home. It's then that authorities found the girls' bodies.
The girls had been seen last in 2015, according to People.
Nicole was 6 when she died and Jasmine was 4, police believe.
The oldest weighed only five pounds when she died in May 2016, Snyder estimated on Wednesday.
When asked in court why she withheld food and water from her daughter, Snyder responded, "So she would starve and die."
She added that she had called 911 when Nicole died, but Echo and Michele Butler stopped her. Snyder said she called 911 again to claim her child accidentally called.
Snyder testified that Echo Butler dug a shallow grave for Nicole. They put mothballs in the girl's body to hide the odor, she said.
After Nicole's death, Snyder said that she, Echo, her son, and Jasmine moved out. She said that Jasmine was initially treated well.
"I told [Echo] I couldn't lose another one, I couldn't do it again," she explained.
However, in August 2017, Jasmine died like her sister, weighing "less than a gallon of milk," Snyder told the court.