How did she end up with 20 eggs? Was it because no one picked her eggs so when she went broody that is how many there were or are there other hens with access to the nest? What I would do at this point is candle eggs and leave her the ones that are closest in development. No more than 10. Then see what hatches before she gets off the nest. (If nothing happens this week candle the eggs again). Next time she goes broody please make sure she only has as many eggs as she can cover.
You can pick eggs she will still go broody. I just had one trying to hatch a golf ball

Just return the eggs when she is ready to set.