There weren't any cases of prime ministers in the past in the kingdom. This will be something new for them.
There was too much required from her to get this kingdom on its feet again. Having an assistant to help her with the kingdom's affairs when she is running around in the future would take that load off her.
And for that person, he or she needs to be treated well. So, stealing an idea from another dream she saw, she was going to build a residence where the prime minister would live as well as conduct his business there.
Just like her palace.
This residence was going to be built on the land where the royal market was currently built.
She was going to put the market somewhere closer to the people and not where it was right now. That was another temporary solution to her problems.