"Gemma has no memory of the accident and is in quite a bit of pain . . . Her last quip to her father was 'tell Graham that I'm going to be off for a term'.''
Mr Preston said he hoped Ms Tong would return to school in March but they had a contingency plan.
He said Ms Tong was very much part of his family.
He first met her at a Christian camp in the South Island when she was in Year 8. Mr Preston told her he believed God wanted her to be a teacher.
Ms Tong went on to train to become a teacher and has lived with Mr Preston's daughter for the past five years. "She is just a gem.''
Mr Preston has been involved in Christian education for 26 years and of all the teachers he had worked with, he said he would rank Ms Tong in the "top 5 per cent''.
Meanwhile, Mr Preston's granddaughter Amy Bell, 17, who was also in the van and escaped with little injury, had spoken to her parents and told them she could not understand why her life was spared as she was sitting in the middle of the van.
Mr Preston said he was still feeling a bit numb.
"What do you say? ... It's very very difficult and very sad for all those who survived and those who have lost.''
Mr Preston said the van had been paid for with funds raised by the group. The hospital where Dr Johnston had been taken was the same hospital he had previously helped in on three occasions.
Mr Preston said he was relying on his Christian faith to get him through. "Faith is the opportunity for God to arrive and he does.''
He had nothing but praise for the New Zealand Government, New Zealand's High Commission in South Africa and Egypt, which was sending deputy high commissioners to Kenya, and the travel agency which had sent a staff member to Kenya to get the group back to New Zealand.
Mr Preston said he expected some of the group would return home on Monday.
Bethlehem College principal Eoin Crosbie met parents, relatives and friends of the group on Wednesday night.
About seven of the group in Kenya remained in hospital in Kisumu with injuries ranging from superficial to more serious, but none was life-threatening.
A Ministry of Foreign Affairs and Trade spokeswoman said the process of repatriating the bodies of Dr Johnston, his wife and Ms Dickson was under way, but a timeline for their return to New Zealand was still to be confirmed.
Yesterday morning friends of Ms Dickson, 19, former and current students gathered at Bethlehem College to pray.
A prayer service was to be held last night for the Johnstons.