The entire internet has no brain, or reasoning ability, and yet it's users have access to vast information. Just because she doesn't know how to apply the knowledge doesn't mean someone else wouldn't know how to get to it.
People who know she exists for sure:
Mab
Molly
Lasciel
Alfred
Bob
Maggie Jr
That secret could easily get out, or be traded away. Chances are good that Vadderung, Hades, or anyone else who throws around massive power, and be able to sense it in Harry knows.
Add Murphy to the list, and probably also Anduriel/Nicodemus.
