Miranda s flat in Manhattan going from "huge" to Little?

When Miranda buys her APT the woman from the agency even asks her of She Is married and has Kids , cause the house Is so big, and if She actually wants to look for less big houses (which no agent said ever)

We Also see her walking around the house and there are quie a few Rooms . Then the house shrinks to the point Miranda can" t even move in It . And has to move out ​when Brady Is still a toddler ????