Ainsley wanted to make a full map of the whole church, but unfortunately, her radar range wasn't that wide.
That's why, when she used her radar ability, she could only create a 3D map of the church's front area, which included the main hall where they usually received the guests and several praying altars.
So far, she didn't see anyone at those places. Thus, she had to sneak in first before expanding her radar range.
And this is where her luck armour played a part. With her luck getting a significant boost, Ainsley managed to find a window near the church's main hall with a rusty lock.
Ainsley tinkered with the lock for a bit, and she could immediately open the window. The window was large enough to fit a child, and it was also located near the ground, typical of windows in this world.
From the 3D map, Ainsley knew that the main hall was on the first floor, yet there are the second and third floors.