Online, Semiramis is often described as "semi-legendary", "semi-legendary" (again), plain "legendary", "semi-mythical", "semi-mythical" (again), and even plain "mythical"—which could lead one to suppose that she never really existed and/or wasn't very important.
It was only re-established in 1910 that she was a real and important person: her real name was Sammu-ramat and she was the co-founder of Babylon with her husband Nimrod (or Ninus). That information kind of improves her credibility, doesn't it? The mythical part is that legend describes her as a goddess and she also figures as a false idol in the Old Testament.
One of Christianity's strongest legacies to western culture is our rabid mistrust of anyone who claims to be (or is described by others as) divine. Horror of idolatry is enshrined in the Ten Commandments and the Old Testament describes countless disasters caused by idolatry. This site quotes two incidents concerning Semiramis as a false idol as told in Judges and Jeremiah.
So Semiramis' acceptability to us is undermined twice:
It is important to remember that these suggestions are manipulative and irrelevant. On the other hand, it is true that Semiramis was the co-founder of Babylon and that she oversaw many elaborate building programs. Those considerations lend weight to Ctesias' and Clitarchus' contention that she was the creator of the Hanging Gardens.