The Chapel Street store has remained shut since the incident on January 13.
It will undergo a refurbishment and reopen on March 19.
Tui said the decision had been taken following extensive consideration and consultation with the local team.
Helen Caron, director of distribution and cruise for Tui UK & Ireland, said: “The events at the Southport store shocked us all and we’ve continued to offer support to everyone affected.
“The decision to reopen the store following the tragic incident was made by the store team who have been very involved in the entire decision making process, with all team members returning to work.
“We would like to extend our thanks to the travel industry and Southport community for their continued support.”
Cassie’s family said: “Cassie has been thought of every step of the way and that means the world to us.
“Cassie loved her job, her regular customers and her work colleagues who became great friends.
“The Tui store is where she laughed and smiled and we would like Cassie’s amazing personality to remain a treasured memory within the Southport store.”