She was the boss in the Northern District of California. US Attorneys are like District Attorneys except they work for the federal, not state, government. The only people with any authority over these attorneys (there are only 93, one for each district except Guam) are the POTUS and Attorney General.
In either case it was ultimately her decision. Following orders is not an excuse for unethical behavior.
You mean, "refusing POTUS's orders to undermine the law of the USA, is unethical?"