Alanna was one of the two elf children in Ellesméra, at the time of Eragon's second visit, as having an elven child was seen as a great vow of love and was not done often. Alanna was 12 years old, and the only female elf child met in the Inheritance Cycle. The other elf child was a male named Dusan, which Alanna was first found with. Alanna was first spotted with Dusan in the chapter "Mind over Metal" in Brisingr, along with the Werecat Maud, as they watched Eragon and Rhunön form brightsteel into a sword.
She was described as "extraordinarily beautiful" with "solemn teardrop faces", and was so far the only character we have met who was both immortal and close enough to Eragon's age to have an acceptable relationship with him. However, she was not, as far as we know, of noble birth, and thus was unlikely to be the love interest prophesized by Angela the herbalist.