If you're still curious I know the answer to this one, shamelessly pilfered from UESP if you want to look up the exact dialogue.Best outcome is to destroy the horn. If it was saved, well, you run into her later and... "I shouldn't have kept Phalevon's horn! Minotaurs can sense, smell, or somehow see it, even if you don't blow it. One set upon me halfway to Gideon. I threw the horn into a bush and ran. I barely escaped with my life. And many bruises!"
I destroyed the horn on my character, so this is second-hand knowledge.