Lori Luthor is the daughter of Lena Luthor, the niece of Lex Luthor and the granddaughter of Lionel Luthor. Lori grew up with her invalid mom and her distant dad so she always had to take care of Lena.
When Superboy was flying around Smallville he heard a girl complaining about her bike,
when she fixed it she broke a nail and then she started to complaining about the bridge. While walking along the bridge it collapsed and Superboy flew in to rescue but Krypto beat him to it. Superboy also asked Lori if she needed anything and she said she needed to go home.
Later, she assaulted a pharmacy to steal some medicine for her mother, but she was stopped by Superboy and Krypto. Superboy offered to take her home and when they were flying she kissed him. That evening she received a visit from her uncle, Lex Luthor, he appears with Kryptonite in his hands claiming that he can cure Lena. Lex cures Lena but then undoes his cure just to prove to Superboy that he has the ability to cure diseases thought to be incurable but is unwilling to help the world until Superman is dead.
Nowadays Lori is with her mom under care of the Wayne Enterprises doctors.
When Smallville High was seemingly being attacked, all the students passed out except for Lori and Superboy (in his Conner Kent guise). Conner felt like a Kryptonite dagger was being shoved into his forehead. Barely able to focus, Conner changed into Superboy as Lori watched from outside the classroom. She had suspected Conner was Superboy but didn't think it could actually be true. She's determined that he doesn't find out she knows since things are "weird enough" between them.