You can't, but you can change the resources that you get from it, and you can change it so that you can build them. But I think it is hard-coded in there that they are irremovable

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If you don't like Santiago, you can just take all her files (Santiago.txt, etc.) and stick them in a seperate folder (in case you change your mind and wish to re-admit her to the game), then go into alpha.txt and remove all appearences of Santiago (be sure and keep the origonal alpha.txt somewhere for backup porposes).