If she's already been sitting that long I imagine she'll give up pretty soon on her own.
For future reference, it's best to break them immediately if you don't intend for them to hatch, as broodiness can be hard on their bodies and can cause some flock strife. Lock them in a wire crate (or I use an isolation pen) with food and water for about 72 hours, then if they're not showing obvious broody signs (puffing up, low cluck cluck cluck, etc) you can let them out and see where they go. If they go back to the nest at any point, lock them up another 24 hours, then try letting them out again. Until they stay off the nest, they don't get to stay out.