Responsa על כתובות 95:9

b) Q. After A died L took over, and managed, his estate. Why, then, did you write that the estate was considered, nevertheless, to be in the possession of the orphans?
A. R. Hananel decided that the estate managed by the widow is considered to be in the possession of the orphans. The widow is merely a managing trustee. Therefore, all the profit accruing because of her management, belongs to the orphans and she can not collect her ketubah therefrom. When the widow demands her ketubah she loses her right to receive her sustenance from the estate. She must, then, take an oath while holding the Scroll of the Law; and whatever she thus states under oath to have given away, or to have retained for herself, to have given to her daughter, or to have given to charity, is deducted from her ketubah.