@mary_here this is just my thinking and im sorry if it doesn't make sense because i have just starting reading this
even if she had money she hasn't found a town or city and theres also the possibility that that the girl's memories doesn't know what currency looks like since shes a orphan
if you're talking about cooked meat food then its possible you cant make living structure since "meat" is a part of a living animal but rice or water insnt a living thing so its possible to create it (hope it makes sense)
creation magic consumes mana (obviously) and she said that she doesn't have much mana to begin with so making a house purely out of creation magic would not be enough to create a house and she said that having materials to build something can make the mana consumption cheaper so maybe if she makes materials to build a house its possible? (idk)
hope its easy to understand ^-^