Are you talking about St. Mary's Canossian School?
Does your daughter have an older sister studying in St. Mary's at present?
There is coverage of school bus over 德福 but not sure about 官塘, 黃大仙 and 油塘. Maybe you can give a call to Ms. Yeung at 82076263 to ask about details of the bus routes.
Competition is keen but I think there is still a chance with 20 marks at 1st round. I tried St. Mary's for my daughter at 1st round last year even with 15 marks. She is admitted by St. Mary's at 2nd round this year.
Wish your daughter good luck and hope she can be my daughter's schoolmate next year