Christina and Saint-Exupery's Fox

When Christina says to Charles, “Chigger, the French say that the heart can see what is invisible to the eye," what exactly is she referring to?

Christina and the Fox, The Wrong Way to Feed a Unicorn

From The Wrong Way to Feed a Unicorn:

Christina took both my hands and looked into my eyes. It was a little creepy. “Chigger, the French say that the heart can see what is invisible to the eye. Here’s what mine sees: You need to find truffles more than the unicorn needs to eat them.

What exactly is Christina referring to?

She paraphrased The Little Prince by Antoine de Saint-Exupery:

Goodbye," said the fox. "And now here is my secret, a very simple secret: It is only with the heart that one can see rightly; what is essential is invisible to the eye.

I wonder if Christina knew what she was saying and how similar she was to Saint-Exupery's fox. Both saw themselves at odds with the world around them and both had a place to hide when they needed it (the fox a cave, and Christina the Flats). Both had insightful perspectives on the world in their own way.

I also wonder this about the fox: He was eventually tamed, but did he stop desiring chickens?

(An aside: Last weekend I was rummaging through the stacks of boxes in my basement that hold books I've read, and I came across three copies of The Little Prince: one in English, one in French and one in Spanish. It's an awesome book no matter what language you speak.)