I don't know what Rose is planning, maybe there's really some plot, or maybe it's just taking responsibility individually. If you dismantle the school's Array, you have to compensate the school with one.
In short, at Rose's request, Hilia agreed with Blake to help design the school's Array, while retaining the Seven Towers.
However, she could only help with the design; she couldn't implement it because she still needed to go to the ancient ruins.
Another important reason is that if people saw her directing the reconstruction of the school's Array, the calm school life might be gone forever.
The same goes for the Holy Court. Hilia didn't want to face Mr. Alvis.
So, Hilia spent a day sketching a rough plan and process for the Array reconstruction for Blake.
After finishing, Rose said, "Give this to that bishop, he will know what to do."
Hilia replied, "Will Mr. Alvis just throw this away like it's trash?"
