On the Bold and the Beautiful, who did Steffy try to run down a few years ago? Was it Thorne's daughter? I can't remember her name.?

Steffy didn't try to run anybody down, it was the other way around. Alexandria (aka Aly), Thorne's daughter, went insane and tried to kill Steffy multiple times: First she tried to run Steffy down with a car (after first flattening Steffy's tire and following her), then she tried to kill Steffy with a tire iron and finally she tried to bash Steffy's head in with a rock, leaving Steffy no other choice but to hit her with the discarded tire iron causing Aly to hit her head and die. It was pure self-defense.

It was Ally that she tried to run down..

Yes, Thorne daughter "Aly" and she died because of it and she also try to kill Ivy by pushing her against electrotype devices down in the basement of that build they works in, but Ivy survived and left to go back to Australia, once in a while you will see her come back to do a scene.