Some possible reasons she would refuse to answer the question are:
1. She doesn't understand the question
2. She understands the question but she knows it's a trap set by evil conservatives who want to enslave women.
3. She feels that people under 3 feet tall aren't human because they can't reach the levers in voting booths
4. Labeling people "human" is a vicious kind of species bias. Everyone has the right to decide for themselves whether they're human or not.
5. Unborn babies can't be human because they have no fashion sense whatsoever.
6. Unborn babies are more like starfish or groundhogs or something. They contribute nothing to society and did I mention they can't vote?
7. It's interesting that fully half the time, men are the ones who ask this kind of question. Men can't seem to accept the fact that only a woman can create a human being. Of course, that's not to say that it is a human being, until it's designated as such by the State.