Toronto police said the Grade 9 student was trying to cross Neilson Road south of the intersection with Finch Avenue East when she was struck.
Diljohn died at the scene.
The collision remains under investigation. Both the Toronto Transit Commission and the bus driver are co-operating with police.
The vigil is expected to start at 5 p.m. ET at the intersection of Neilson Road and Finch Avenue East.
A fund has been set up at a Malvern Scotiabank to help Diljohn's family pay for her funeral.