Johnson saw the message and said: "Be my privilege to have her with me and dedicate my performance to her when we play in Brisbane. So sorry for your loss, awesome to see the photo of her in action doing her 'johnson skip' ha."
Lisa's sister Hannah Penina Mapu 20, told the Herald the family were shocked when the Kiwi NRL star Johnson replied to the message.
"We didn't think he would reply.
"We were just wishing and hoping. It's so surreal for us."
Ms Mapu said Lisa had a bucket list that included travelling to France and eating crepes, to wanting to watch Johnson play live.
Her and her six brothers wanted to finish Lisa's bucket list when she passed.
The Samoan Observer reported last month that Lisa's family had set up the Lisa-Bridget Mapu Foundation in her memory. The foundation had donated computers, books, printers and stationary to Vaimauga College in Samoa.
Ms Mapu told the newspaper: "Lisa had a heart for helping others less fortunate than herself which urged her to build her dream of helping Samoan students by providing the necessary resources for the bettering of their education," she said.
"Lisa had planned on donating resources and supplies to a school that she could see would use and need these, so that she would be able to make it an ongoing alliance to help and improve the education status for Samoa."
An NRL spokesman said Johnson was still in the process of planning a dedication to Lisa and it was too early to say what he would be doing.
"The game is still two weeks away," he said.