Have part of it fashioned in to a goblet. Any liquid put in the goblet is purified making it safe to drink. She can keep it or gift it to someone. Powerful leaders often worry about having their drinks poisoned.
I have a neat kids book called the Sorcerers Scrapbook. A mean noble is paranoid that someone is trying to kill him because the sorcerer plotted his astrological chart and discovered that the Duke would die of poison. The rest of the book is about the sorcerer trying to find a unicorn.
It would be a cool story adventure if a similar duke character found out about the horn and wanted to acquire it by any means.
Spoiler book: they find the unicorn and the horn and find out it sheds its horn every 1000 years. The Duke gets his unicorn horn goblet but Is still assasinated by a poisonous arrow. The stars never lie.
Also, on a separate note, because she has a piece of the unicorn, one day, if she gets enough money, she could have the unicorn rezzd