The attack, which the family claimed was carried out following a longstanding rivalry between two villages, took place on Tuesday morning.
Police are yet to confirm their allegation.
Pabna police OC ANM Abdullah Hasan identified the deceased as ‘Samiran Bewa', wife of Taju Pramanik of Balarampur village in Sadar Upazila's Dogachhi Union.
She died at Pabna Sadar Hospital around 9am on Tuesday, according to her daughter-in-law Reshma Khatun, 25, who was also injured in the attack.
Samiran's body was sent to the morgue for autopsy, said OC Hasan.
Reshma, who currently being treated at the hospital, said a bomb was hurled at them when they were on way to the toilet outside their home early in the morning.
“Family members took us to the hospital. My mother-in-law died at 9am while under treatment,” she said.
Reshma said someone from Char-Balarampur village may have carried out the attack following a feud that had been continuing between villagers of Balarampur and Char-Balarampur for long over establishing supremacy.
OC Hasan said: “Its clear that Samiran died from the bomb blast. But the motive behind the attack is not clear yet. We suspect old rivalry might have been the reason. We are still investigating."
He said police could not collect the evidence from the bomb attack from the spot as a large number of people had gathered there.