Gillian Millane and Hannah O’Callaghan, Grace’s cousin, were named Officers of the Order of the British Empire (OBE) for the charitable work they did to stop violence against women after Grace’s death.
They were among more than 1200 individuals named by the British government on behalf of King Charles III for exceptional achievements and public service.
In comments reported by the British media, the pair said they were surprised and humbled by their awards and thanked those who nominated them. They dedicated the OBEs to Grace, who they said would be proud of the impact that their charity, Love Grace, has had.
"I don’t think she would believe how big Love Grace has become and how many women we can help by offering a bit of normality to," O’Callaghan said in a statement reported by the PA Media news agency.
"She would have also probably been amused that we have been to Downing Street and are now to meet a member of the Royal Family."
Gillian and her niece Hannah started the charity four years ago, through which they collect donated handbags and fill them with toiletries for domestic abuse victims. To date, they have filled 15,600 bags for women in the UK and across the world.
Next year, she intends to apply for Love Grace to become an official charity.
O’Callaghan added: "We wanted to create a legacy in Grace’s memory and directly help women who have been affected by domestic abuse, to turn our negative into a positive.
"If we help just one woman, then we have achieved that.
"We have been overwhelmed by the support people have shown our ‘Love Grace Handbag Appeal’, from donating handbags and toiletries to running appeals in their own area.
The OBE comes days after Gillian Millane said in an interview that she was plunged into darkness after her daughter’s death and at one point contemplated killing herself.
"Grace had such a bright future and it was taken away from her and us," she told the BBC.
"I will never see Grace in a wedding dress or see her grandchildren. This is a life sentence I’ve got. This is me until the day I die."
But she said she eventually found the strength to keep going. "I will never get over it but I just know I’ve got to make the world a better place," she said.
By Alex Spence