Could be Dawning 9 by Debby Stark. I just used the Archive's search feature to look for "harvester" and this seems to fit with what you described.

http://www.lcfanfic.com/stories/dawning9.txt

Fanfic | MVs

Clark: "Lois? She's bossy. She's stuck up, she's rude... I can't stand her."
Lana: "The best ones always start that way."

"And you already know. Yeah, you already know how this will end." - DeVotchKa