It may well be that Hillary doesn't care about immigration. In fact, it's likely she doesn't but we cannot know. On the other hand, we know for certain that Bush doesn't care.
Very few in Washington care. The only thing that brings it to center stage is people like Stein report, American patrol, and Congresspeople such as Tom Tancredo.
P.S. the only reason she's talking about it is because it is opposing to what Bush is talking about.
She has probably seen polls on the topic too.