This is kind of a cross between a logline and a tagline.
Why twins? Why not just one person? If it has to be twins, why is just one fighting back? Why not both?
"one finally decided to fight back"... how do they fight back? What do they do? A logline should give the reader a clear idea in their head what is happening. Since you put this in the Horror genre, I'm guessing it's something grisly, but what? Does she hunt the racists down? Does she summon the dead with voodoo? Give us some specifics. Same with the harassment actually. What do they endure? Does someone shout names? Or do they get beaten up? Are they black and they've moved to a former confederate state? More specifics would make a big difference in understanding this story.
Don't put things in brackets. It makes it seem like a secondary thing whereas actually, the fact it's a film about racism is fundamental to understanding the whole concept.
Films like 'Get Out' have shown there is definitely a market for a racially motivated horror film so I'm intrigued to see where this goes.?