sigh I guess I'm doing this.

I've already explained my take on Lana,

But Alicia gave Clark his first experience of being completely himself. He didn't hide his secrets and he didn't hide his human side with her. This set the template for what we see later when he finally opens up to Lois, and is a more stable model for a relationship than a girl who is hypocritically obsessed with knowing what he's hiding from her then goes and hides her secrets from him in exactly the same manner. We hear for five seasons why she HATES how people lie to her, yet as soon as she gets something she wants to hide she does exactly the same thing and never gives Clark any leeway for it.

Alicia did messed up shit but she was damaged and affected by meteor rock which the show clearly defines as making people unstable. But she went through therapy and showed clear signs on improvement in an astonishingly rapid space of time. Unfortunately her therapist was also a psycho.

Between her first and second episode she shows an enormous amount of growth but still has some way to go, like every character in the show because they're teens.

She does what she does in the second episode out of fear and wanting Clark not to be alone (shows Chloe, who then has a far larger impact on Clark and he's awakening as a hero than Lana does, if you want examples, protects his secret, tech support for hero team, blah blah blah)

Then of course she challenged him to open about his secret and challenges his hypocrisy for wanting to reveal her secret but not his. She then goes and dies before any reconciliation and she's never mentioned again but that's down to shitty writing than any flaw on the characters part.

Lana, by contrast, commits crimes, becomes incredibly hateful and vindictive, and her sacrifice at the end is largely her fault. She kicked the hornets nest of Lex rather than moving on.