[@TheWindel]

Only one jewel is designated for her shields out of twenty (I just made that edit)

If she uses up all her slots she has to sign over the property to another owner before that jewel is able to be used for another structure (just made that edit as well)

[@KoL]

Its total floor area also she doesn't create these structures herself she has to get places that are already built.

A part of the way she written is that her magic is supposed to be for the protection of others instead of herself so it's stronger when her magic is being used in a way that puts someone else's life above her own