But prison wardens allegedly allowed the beating to happen without intervening.
“During the course of this unconstitutional assault, not one single jail guard or official attempted to stop the attack, intercede to prevent further abuse or offer medical assistance to Ms Rathmann,” the lawsuit says.
The 33-year-old mother-of-one was only rushed to hospital after guards later found her “unresponsive” in her cell, the document states.
She died two days later, on 23 August 2018, after suffering a “massive” stroke and bleeding on the brain. Her death was listed as “natural”.
But the lawsuit, filed on behalf of Ms Rathmann’s father Kent last week, will now seek to have that verdict overturned, the appeal website reports.
He is requesting the state award him at least $3m [£2.3m] in compensation for what he says is the violation of his daughter’s constitutional rights that caused her death.
And he will say the beating she received was not the first time she had been targeted – citing a similar incident in which another inmate smashed her over the head with a phone.
Carlos Moore, attorney, said: “Unfortunately it’s too late for Ms Rathmann, to bring her back, but her family would like to see justice and Mississippi Department of Corrections be held accountable for the inactions that led to her death.
“They would like to see systemic changes, and of course they would like to be compensated for their pain and suffering.”
He added that Ms Rathmann was due out of prison on parole just five days after she died following a six-year sentence for selling methamphetamine.
The MDOC has said it will not comment on the issue while litigation is pending.