LovelyLocks is a serum that makes your hair "lovely." Biana brought some with her to Rimeshire when Sophie, Fitz, Dex, and Biana had a sleepover together in Lodestar.
You can find it at Slurps and Burps.
A human version of LovelyLocks is Moroccan Oil, it works wonders.
There was a bottle of Raven LovelyLocks found in Jolie's room at Havenfield.