There are literally so many Bellamy Blake fanfictions that immediately make the OC hate Clarke. Like, sure, your OC can hate Clarke as much as she wants, but make it mean something.
If Clarke was the reason a friend or loved one died, then sure, maybe the OC'll hate her. If Clarke lied to the OC about something important, maybe they'll hate her.
But if the OC hates Clarke because she thinks she is in love with Bellamy, that's crazy. The OC should never go batshit crazy over something like that. If the love interest is Bellamy Blake, then Bellamy can still fall in love with the OC without completely destroying Clarke's character.
Clarke is compassionate. She thinks with her head, she loves her people so much she'd kill and die for them. She's not some jealous girl that will try to steal Bellamy from the OC, so stop making her out to be.