Jennalla Deemspring

Jennalla Deemspring was a high elven ranger. She was stationed with a small group of high elven survivors near the ruined Lordaeron palace gardens when the death knight Arthas returned to Lordaeron, took back control of the kingdom, and ordered the Scourge to exterminate all remaining survivors. Arthas, along with Kel'Thuzad and Sylvanas Windrunner, may have come upon Jennalla and made quick work of her and her brethren.

Trivia

 * In Warcraft III: Classic, she uses the same model as Sylvanas, the only difference being the color of her team making her cloak yellow.
 * Jennalla Deemspring is named after Jennifer Deem, the then-girlfriend of David Fried, level designer of the mission she appeared in.

Speculation
Whether she and her elves were high or blood elves is unclear but it is possible that they were high elves who were not in Quel'Thalas when Arthas destroyed it; or they could be elves who didn't accept the sin'dorei name. Alternatively, she and her brethren could have become the sin'dorei and left the elven kingdom afterwards.

It's also possible they weren't even full elves at all, since the Ranger model that Jennalla was based on was intended to be half-elf.