From the pilot episode Liz was written as being very intelligent, managing to work out how to run a DNA test, after Max saved her life, in order to find out how it was possible that he could have done it with just a touch from his hand.
She’s a very determined but kind hearted person, something that exists in the character throughout the three seasons. I liked the fact that the writers didn’t make her the archetypal good girl, who never made any mistakes, as she rebelled against her father, and had a tangled relationship with Kyle. Kyle was her boyfriend for a portion of the first season, until, driven by jealousy over her emerging bond with Max Evans, he and a group of his friends physically attacked Max.
She took her protectiveness of her friends, and her determination to solve mysteries to a whole other level during the second season, when Alex Whitman, one of Liz’s best friends was killed. She isolated herself from the three alien characters, by her insistence that Alex’s death was somehow related to their extraterrestrial origins, but was ultimately justified.
The third season was the most interesting in terms of Liz’s character development though, as she received alien powers. She became able to see the future, with certain people just by touching their skin.
She’s remarkable, especially for being a teenager, the writers’ making her selfless to the extent of sacrificing her own happiness on more than one occasion, such as the second season finale, where she was willing to let the most significant romantic connection in her life go, for the sake of his son.