Like all Whispering Deaths, the mother is extremely aggressive. However, she does have a maternal side as she knew the Screaming Death was her offspring despite not being present when it hatched. She was very happy to be with her offspring.
She also seems to trust Hiccup and Toothless as they reunited her with her family and tried to help her when Dagur captured her.
The Outcasts placed crates of the mother's eggs under Berk in an attempt to destroy the village. The offspring attacked the village in Tunnel Vision, but were chased off by the Dragon Riders.
The mother made her appearance along with more of her eggs, children, and her possible mate. Hiccup realizes then that the Screaming Death was destroying islands trying to find her.
Alvin releases her, and the other Whispering Deaths during the fight with the Berserkers. Fishlegs leads the Screaming Death to the island, which the mother immediately recognizes her child. Dagur and some of his men capture her and threatens to kill her unless Hiccup hands over Toothless. Thankfully, Snotlout and Hookfang show up and free the mother. She and her offspring reunite with the Screaming Death and the family leaves Outcast Island together.
Dragons: Race to the Edge
It was revealed she had been living on an island along with the Screaming Death, and possibly her other children. And while the Screaming Death did not remember Hiccup and Snotlout, she did. The mother defended them when they came to island from her large offspring, allowing them to take some of the Screaming Death's shed scale to make armor against the Dragon Hunters' arrows.
Alpha: Being the mother of her family she shown to have complete control over them and including the Screaming Death.
Intelligence: She have shown to be able to remember her saviors from few years ago as able to protect them from the Screaming Death.