When they had done this is omitted by Good News Translation as redundant, but it may be perfectly natural style in certain languages.

Judith went out, she and her maid with her: The phrase went out means “went out of [or, left] the city.” The following phrase, she and her maid with her, helps to put emphasis on Judith. Some languages may be able to keep this construction, but other languages will need to follow Good News Translation with “Judith and her slave left the city.”

The men of the city watched her …: The description of the women walking down the hill, into the valley, and out of sight of the men watching from the city walls is effective placed against verse 11, where we shift our point of view and see the two coming from the standpoint of the Assyrians. There is some difficulty with the picture since this is supposed to be taking place at night (8.33; 11.4), but there is not much the translator can do that will not either accent the problem or misrepresent the picture. Perhaps without too much strain, the Greek can be understood like this: “the men of the city kept their eyes on her until she had gone down the mountain and started across the valley and they could no longer see her.” This involves highlighting the beginning of the action passed through. This is permissible and it perhaps clarifies the picture.

Passed through the valley: Part of the difficulty here, and in the next verse as well, is the idea of the women going through the valley. In English, going through a valley implies that one is going the length of it. These women are going across the valley to the opposite side, as New American Bible and New English Bible correctly picture it. In 13.10 the two women reverse this path.

Quoted with permission from Bullard, Roger A. and Hatton, Howard A. A Handbook on Judith. (UBS Helps for Translators). New York: UBS, 2001. For this and other handbooks for translators see here.