In the Etheral mod, GLaDOS was core-swapped with ETHERAL, and so you join her with the adventures of the potato battery once again. She is featured in the second half of the game, while you try to re-core swap yet again. Of course, GLaDOS, when she fell, there was no stalemater, but ETHERAL, being higher ranked (he is the maker of the company and started the human-to-AI fad), got an exception, especialy due to the cores he secretly implanted on her.