Lena's whole arc is basically about resisting a predetermined tragic fate, which gives the story its spine. She's not just the 'beautiful creature' of the title; her struggle with her Claiming, the choice between Light and Dark, is the central conflict. Sometimes her teenage angst and the back-and-forth with Ethan can get a bit repetitive, but I think that's intentional—it mirrors the chaos of her powers and her fear of hurting him.
What sticks with me is how her relationship with her family, especially Uncle Macon, defines her. She's not an orphaned heroine; she's smothered by this ancient, cursed legacy, and her push-pull between embracing her family and defying them feels real. The rating might dip for readers who find her too moody or indecisive, but for me, that volatility is the point. She's literally a force of nature, trying to control a storm inside her, so of course she's not always likable in a conventional way.