The victims were attacked while attending a Taylor Swift-themed event at a holiday club in July.
They were invited backstage at Wembley Stadium during Swift's five-night stand on the final leg of her European tour.
One of the girls' mothers, Sami Foster, posted a carousel of photos on TikTok sharing her daughter's experience.
"The biggest thank you to @Taylor Swift and her mum for making the most magical night possible for us all," she said.
"Thank you for bringing Hope & Autumn pure happiness last night & always."
One of the girls appears to he sporting a bandage on her forearm in one of the snaps - on which is written a lyric from Taylor's Cardigan song that goes: "You drew stars around my scars."
It's not known how many families Swift has met during her London run, but reports say Foster's is not the only one to have been treated to a meet-and-greet the singer.
Swift has not yet publicly addressed the meetings.
It was reported before the start of her five-night run at Wembley she had privately contacted the families of the three girls killed in the July 29 attack – Alice Dasilva Aguiar, 9, Elsie Dot Stancombe, 7, and Bebe King, 6.
Eight other children and two adults were also injured in the assault, with six listed in critical condition at the time.
With AAP.
