That does raise some interesting questions.
I feel that if another artist were to sculpt the figure of a girl and place that on the bull, that would be a clear alteration of the original artists artistic intent. Placing the same sculpture of the girl 100 meters away from the bull, would equally clearly not have an effect on the artistic intent. So where is the line drawn? How close is "too close" At what point does another piece of art start to affect the impression of the first piece of art?
Does it even matter? As previously posted, one artist does not have control over what art is or is not displayed next to his or her piece of art. However, in that context, the two pieces of art are intended to be two individual pieces that happen to be displayed adjacent to each other.
But, in the case of the bull vs girl, the statue of the girl was intended not to stand alone as its own piece of art, but was specifically made and placed to form a new relationship with the already existing statue of the bull.
This, in effect and by design, changes how the original bull art form may be interpreted and changed without the original artists permission.
Does that matter?
Does an artist have a reasonable expectation that once the piece of art is purchased/delivered that the original intent of the artist must be maintained?
Does the artist of the bull have a case that with the addition of the girl, a brand new combined piece of art is now created (bull + girl) and that could be construed as copying the art of the bull into another piece of art?
Can I take any one of any of your photographs, take two of my photographs and form a triptych and call it my own? Does it change if I take two of someone else's photographs and add one of mine to make a new triptych and call it my own creation?
Where does one piece of art end and another one start? Especially when considering the three-dimensional aspect of sculptures.
I can see and appreciate both sides of this issue.