Jordana Johnson, 36, her 12-year-old son Jordan Norris and his friend Chazz Mather, also 12, were killed in the October 15 blaze that destroyed a two-storey home at Gladstone in central Queensland.
It took crews almost two hours to extinguish the October 15 blaze with search efforts for the trio initially hampered by the house's top storey collapsing.
After a week-long investigation, police said they believed the blaze was deliberately lit, charging a 37-year-old Toolooa woman with three counts of murder and two counts of arson.
She is expected to face a bedside hearing in hospital on Friday.
The devastated family spoke publicly for the first time earlier in the week as the Gladstone community planned to remember the trio at a beachside gathering.
"Three beautiful souls were tragically taken from us," they said in a statement posted on social media.
"The impact of this horrific event is being deeply felt not only by our family but by the Gladstone community and across the nation.
"Our lives, and all those that loved and knew Jordana, Jordan and Chazz are forever changed."
The community has rallied around the victims' families, with a gathering planned at nearby Barney Point Beach on Saturday.
Ms Johnson was remembered as a devoted mum with a big heart whose children were her world.
Her son Jordan was "fun, playful and cheeky" and protective of his family and friends.
His mate Chazz was described as an outgoing "loving soul with a cheeky attitude".
The fire is believed to have broken out while Chazz was visiting for a sleepover.
Police are expected to provide a further update on the investigation on Friday afternoon.
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