This is what people are talking about when saying not to bash down ENFPs ideas and just tell that their view is retarded. I mean if you would respond to her interest on astrology(and other stuff) the same way as i answered to you, she would most likely respond to you differently.
edit. also one crucial aspect you need to be aware of is that this ENFP might had noticed subconsciously for example that many people who first started learning about the world during summer are different from those who first started learning in winter, but not be able to consciously get an reason for this, since it might be perceived through intuition. astrology might correlate with this intuition of hers and she starts to believe in astrology. if you just respond with "astrology is full of horse shit", that goes against her intuition, and as an Ne dom, she will have faith in her intuition. So a better way would be to find a reason for this intuition with something i explained above.