Lydya had also reported to the police in December, claiming that her husband had beaten her. He had also threatened her with a gun on another occasion.
Mexico City Chief of Security Omar Garcia Harfuch said Hernandez met with two people at the restaurant at 14pm last Thursday, before leaving around 00pm, according to the Milenio news network.
Lydya later arrived at the restaurant and shots were reportedly heard after she and her husband started arguing.
Hernandez and his bodyguard are in custody
Hernandez and his bodyguard appeared in court on Sunday and are now in custody as police continue their investigation.
The lawyer, for his part, pleaded not guilty, insisting he did not kill Lydya, who was due to perform at a concert in California on Saturday. Hernandez will return to court on Thursday after his request to be placed under house arrest due to age was rejected by the judge.