Mary Herbert was Philip Sidney’s sister, as educated as he was. She became the guardian of her brother’s literary legacy, but was also a talented poet and translator in her own right. She translated from French, Italian, and Latin. The translation of Psalms was a project started together with her brother, but Philip’s work was cut short by death and she ended up translating most of the psalms. They probably translated from Latin (so it was translation from a translation) – Sidney certainly didn’t know Hebrew, and if he didn’t, it is not very probable that his sister would. She may have been as educated as he was (not a rule in Elizabethan families, where girls often got second-rate education), but not more than he.
Psalm 52 is translated using rather short lines, 6-syllables alternating with 5 syllables, which is a rather interesting choice, given that the Psalms in the English Bible are long prose lines. The psalm condemns the wicked men in no uncertain terms and the terse lines with two accents seem to emphasize it. On the other hand, the speaker is like the olive tree, with its roots in God. One has a feeling Mary Herbert chose simple and direct line for simple message.