The Instagram pictures have now been deleted amid reports Rarri True dumped Chyna, whose real name is Angela Renée White. Rob, 30, accused Chyna, 29, of having an affair with Rarri while they were together.
“Posting online or distributing photos of Ms White’s intimate body parts is a crime punishable by fines and jail time,” the letter, sent by Chyna’s lawyer Lisa Bloom and seen by TMZ, said.
The letter also referenced California’s revenge porn law which prohibits the intentional distribution of “non-consensual pornography” and is punishable by up to six months in jail.
Chyna’s lawyer, Ms Bloom, told reporters she was working with Rob’s legal team to come up with a formal arrangement for co-parenting Dream, the former couple’s eight-month-old daughter.
The deal will involve a nanny shuttling the child back and forth between Rob and Chyna.
“She’s not trying to prevent Rob from seeing his baby,” Ms Bloom said. “She believes a father should stay in contact with his child ... She wants to have a healthy, peaceful co-parenting relationship.”
According to TMZ, the pair “have been operating under an unwritten arrangement where they each are entitled to physical custody 50% of the time.”
Sources told the gossip site the arrangement has been “loose by consent”. Rob has recently looked after Dream four days a week, while Chyna has her for three. Nannies and nurses are always present.
TMZ reports the reality TV star was looking after Dream when Chyna was in court seeking a restraining order against him.