Ash, she certainly can claim that. But that isn’t the default. By default Halacha, any income or assets she comes into possession to during the course of marriage belongs to her husband. Furthermore, if she does claim איני ניזונת ואיני עושה, she forfeits her right to have her husband support her. Critically, as well, is if she does make that claim it is only effective going forward, not retroactively. So any income and assets (other than a small number of exceptions such as gifts he gave her) that she accumulated during the course of her marriage up to and until the point she makes that formal claim, still remain the full property of her husband.
Since the discussion here is about divorce, if she hadn’t previously claimed this before divorce was considered it is of no use to her since up to that point all income and assets belong to him and she can only claim it for future income or assets that she generates.