Kirsty Parker died after her Vauxhall Zafira collided with a Peugeot 207 on the A698 near Denholm on 11 February.
Her three youngest children, who were also in the car, sustained non-life threatening injuries. They have all since been discharged from hospital.
Ms Parker's family said they were still trying to come to terms with her death.
Ms Parker, from Denholm, died at the scene of the crash, while the 26-year-old male driver of the Peugeot was treated for "non life threatening injuries".
In a statement issued through Police Scotland, the family said: "Kirsty was devoted to her family and we are still trying to come to terms with our tragic loss.
"She was a much-loved mum to Jessica, 16, Kyle, 12, Mackenzie, nine, and John Paul, two, and planned to tie the knot with her fiancÃ©, Chris, in September.
"As a family we enjoyed many trips to the countryside to walk, camp and fish and we will cherish these fond memories forever.
"We'd like to thank the local community for all their support so far at what has been an incredibly difficult time."
The statement added: "We understand that officers are still trying to trace witnesses who were in the area at the time of the collision, and would ask anyone who can help police with their inquiries to come forward."
The family of a mother-of-four who died in a crash in the Scottish Borders earlier this month have paid tribute to "a much-loved mum".