Princess Selena of Erebor (and sometimes Mirkwood) is a minor character in the series.
Selena was born in TA 3001 with her twin. Her mother married Legolas, the love of her life in a young age. She is the princess of Mirkwood and Erebor, the sister of Ariana, and the oldest daughter of Alison and Legolas. She was just a child when the battle for Middle-earth began and was one of Hazel and Bilbo's best friends.She was only a child when the War of the Rings happened. In the second Tales of the Mountain, she is a grown woman, helping Hazel in many of her (mis)adventures.
After the war, she grew up to be a strong Elf-dwarf but also was seventeen fighting in the battle near Erebor. It is unknown if Selena went to the undying lands after their struggles were over. Her model is Jennfer Morrison.