From Jay:
I assume she clicked the "Unlock Everything" button and does not have the Developer Map Editor Hack installed. If that is the case, that is not a problem. The download description for the Developer Menu Hack (which is different than the Developer Map Editor Hack) says:
"... When the Developer Menu is closed and reopened after clicking the "Unlock Everything" button, zoo walls, zoo entrances, and admission booths will also be available to add to zoos. However, they should not be used without the Developer Map Editor Hack because they cannot be deleted without a map editor hack and they can cause ZT to become confused if they are added to a zoo, especially for the zoo entrances. If you do not have a map editor hack, their icons in the Developer Menu will be a generic wall icon for the zoo walls and blank icons for the zoo entrances and admission booths. So they should be easy to avoid using. ..."