Why did Helen Bryce try to kill Lex?

[MystV]

I never really understood the motivation. Yes he stole a vial from her but was that the reason?? It just seems too petty to kill someone over. It always seemed to come out of left field to me.

Was she in Lionel's pocket most of the relationship or do we believe her when she claimed Lionel only offered her money to break up with Lex?

[skully]

I dare say Lex's will would've made her a very rich woman. She was a gold digger. Lex "accidentally" dies on their honeymoon, she becomes Miss Moneybags, AND doesn't have to put up with creepy Lex sex!!!

She was clearly paid by Lionel to spy on Lex, but got greedy and wanted it all.

Then again, she didn't reckon on Lionel defending her son's honor.

[Jennsen]

That's simple: she wanted complete control of Lex's money. Though you're right that it came out of left field, but that's just bad characterization, which is something you just have to accept if you want to watch Smallville.

[DJ Doena]

Simple: the season was over, they wanted to abandon that plot, so they did it in the crudest way possible, to have her make a face-heel-turn

[Dagenspear]

It may seem strange, but when I watch these episodes, I kinda get the impression that she was protecting Clark.

[jon-el87]

That's simple: she wanted complete control of Lex's money. Though you're right that it came out of left field, but that's just bad characterization, which is something you just have to accept if you want to watch Smallville.

Not so sure about that. She first appeared in "Dichotic". She first meets Lex at the medical center. Then she just happens to show up at the same anger management class as Lex. She asks what he's there for. Clark previously made it clear that everyone in town knows about what Lex did, because there's a reason the town's called "Smallville". Yet, Helen claims to be oblivious. He asks her out, but she turns him down. Later, Lex asks her out again, but she's reluctant for a few minutes, then agrees. In "Visitor", she's reluctant to move into the mansion, but then gives in.

Looking back, with the idea that she's out to get his money in the back of your head, the whole thing becomes suspicious. In "Dichotic", Helen says that she and her dad (who is identified as a high-profile plastic surgeon in Metropolis) stopped talking, after she refused to join his practice. We only have her word for that. Maybe dad cut her off, forcing her to work at places like the Smallville Medical Center, then she meets Lex and sees an opportunity to strike it rich. She arranges a second chance encounter, where she rejects his advances. After all Lex is a rich kid, who's used to getting whatever he wants. By turning him down, she turns herself into something he can't have. Ensuring that he must have her. Prompting him to go after her again, where she "reluctantly" agrees to go out with him. Then she pretends to be unsure about moving in with him, ensuring that it'll be his idea that she moves into the mansion. His idea, not hers. Then they get married, again something Helen is "unsure" about, and Lex dies in a tragic accident on the honeymoon. Leaving her with all his money.

She always was evil, just very good at hiding it. She didn't throw herself at Lex, but played the role of the unsure girlfriend. She didn't instantly move into the Luthor Mansion and start spending his money on clothes, but pretended to be uninterested in money and reluctant to move in with him.