We may suppose that she gathered these memories normally, but this is only a supposition—there’s no evidence of any normal channel through which these memories could have come.
Moreover, Sukla didn’t just recall information—she actually recognized people, people who in this life were complete strangers.
She recognized Mana’s mother-in-law from a group of thirty people. She pointed out Mana’s brother-in-law Kshetranath, and she knew his nickname, “Khetu.” She also recognized another brother-in-law, whose nickname was “Kuti.” But she identified him correctly by his given name, Karuna, which even his neighbors didn’t know.
She also said that her first child, a son, had died while still an infant. This was true for the life of Mana. And Sukla tearfully recognized Mana’s daughter, Minu, and showered her with affection.