The Princess Elizabeth paid a private visit to Comber in 1946 to stand as a Godmother at a Baptism.
Have you tried the Court Circular archive?
Belfast 19 March 1946 to launch a ship at Harland and Wolff
May 1949 with The Duke of Edinburgh
July 1945 with The King and Queen on the Victory Tour
The King and Queen visited NI in 1942 but I don’t see any evidence of Princess Elizabeth accompanying them.
Hillsborough Castle have lots of photos of Princess Elizabeth visiting the Castle.
The present Queen’s late Mother, Queen Elizabeth, was a sister of The Countess of Granville (wife of the Governor of NI from 1945-52) and they visited her at Hillsborough Castle on a regular basis.