Welcome to BYC. As others have shared, not all breeds, and not al birds from a 'broody' breed will set and incubate eggs. For hatchery sourced breeds the instinct has been selected against as maximum egg production is the goal. Sounds like a great excuse to get an incubator. Is she pulling feathers and lining the nest with them ? That can be an indication of impending broodiness.
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She is sitting on them now, I locked them in their run and not letting them free range. Hopefully this will help
Are all of your ducks locked in together, or just your broody? You might want to candle the eggs under her to make sure they're fertile and developing, but since this is her first go-round, maybe reducing her brood to 8-10 would be more manageable. Also mark those eggs so you can remove any that other birds may add later. If they're not all at the same stage of development, she'll probably abandon the rest after her first ducklings hatch. Good luck!