From Smallville to NXIVM

You can see the path taken by Chloe from episode one of Smallville that ended with her joining that dodgy sex cult:

Chloe's unrequited love for Clarke. This made her clingy and needy, which is just how Raniere liked 'em.

Her jealousy of the beautiful, perfect Lana. All the boys loved Lana. Only the freaks liked Chloe. This gave her a deep-seated inferiority complex that making her a perfect candidate for NXIVM brainwashing.

How betrayed she felt by her 2 best friends. This exacerbated her insecurities.

Also, her body was not as "ideal" compared to 90% of other cast members, so she was constantly body-shamed for years. No wonder she took to branding other women. It was her way to get payback, to get ownership and empowerment.

Yes, Smallville has a lot to answer for how Chloe turned out.