A Queensland mother cleared of killing her son with a drug-spiked smoothie has been charged with murdering her daughter.

Maree Mavis Crabtree was found not guilty on May 11 of killing her son Jonathan, 26, after his body was discovered in their Gold Coast home in 2017.

Crabtree, 59, was accused of preparing a fruit smoothie spiked with the prescription drug oxycodone before making a $125,000 insurance claim from his superannuation death benefit policy.

At the start of the five-week trial, Crabtree pleaded not guilty to murder, attempted murder and fraud charges. The jury found her not guilty on each charge.

Crabtree walked free from Brisbane Supreme Court, after becoming emotional as the jury's verdict was read out.

However, it can now be revealed Crabtree must return to court to face a murder charge over the death of her youngest daughter Erin.

The 18-year-old was found unresponsive inside the family home in September 2012, while the rest of her mother, brother and sister were enjoying a Pacific Islands cruise.

The trip was funded by disability service Lifestyle Solutions to give Erin a holiday, but just a few weeks before leaving, her mother told the travel agent her daughter was not going.

All details of the second murder charge against Crabtree were kept from the jury during Jonathan's murder trial, although the judge referenced her death while summing up. 

'You know from the evidence before you that (Jonathan's sister) Erin Crabtree died some years before Jonathan,' Justice Martin Burns told the jury.

'There is also evidence that her death had an ongoing impact on Jonathan, who continued to grieve for his sister.

'However, there is no evidence before you about what caused Erin's death, but there is nothing unusual about that. The parties do not have to explain every aspect of the family background.'

He added it would be 'quite wrong to go speculating about the cause of Erin's death, because if it had any relevance to this case, you would already know about it.'

After the jury found Crabtree not guilty, one of Jonathan's closest friends launched a GoFundMe to help give her mate 'the send-off he truly deserves'.

'This fundraiser is being created so his friends and loved ones can come together to honour his life properly, celebrate the memories he gave us, and support the people and places that meant something to him,' organiser Kayla-Maree Robb said.

'Despite the weight he carried, he still showed up for his mates, still made people laugh, and still gave support. 

'That's the kind of person Jonathan was - selfless, loyal, and full of love for the people around him.'

Ms Robb said a portion of the funds will also help pay for flights and accommodation for Jonathan's father Mark to attend the memorial.

Funds will also be donated to help the Helensvale Hornets rugby league team, where Jonathan's ashes were previously spread. 

'Every donation, share, and message of support means more than words can explain. Thank you for helping us honour Jonathan's memory and stand beside the people who loved him through this incredibly painful time,' Ms Robb added.

In a Facebook post sharing the fundraiser, another friend added: 'He will be remembered. Never forgotten. We will support Tara too.'

Tara is Crabtree's surviving child who was a witness in the trial.

As well as the murder charges, Crabtree is charged with attempted frauds of at least $100,000 in December 2018, at least $30,000 between October 2010 and June 2015 and another attempted fraud in June 2015.

Crabtree also faced Commonwealth fraud charges at Brisbane District Court on May 22 including eight counts of obtaining a financial advantage by deception between 2009 and 2018, and three charges of general dishonesty. 

Crabtree's lawyer Jodie Mair said the Commonwealth charges couldn't progress until her client's Supreme Court matter was finalised.

'I can confirm that the first of those indictments has been resolved by way of a trial,' Ms Mair said, referring to Crabtree's acquittal on May 11.

Ms Mair said the outstanding murder and state fraud charges are listed for mention or review within the next month. 

'It's the case where these (Commonwealth) matters reasonably can't progress until finalisation of the Supreme Court matters, and largely that may dictate how these matters proceed,' she said.

'As I've indicated the lines of communication are open between… defence and the prosecution in respect of the remaining Supreme Court indictment.'

The Commonwealth charges are listed for mention in the District Court on July 16.