My character is travelling from mainland Europe to Plymouth in late 15th century. She awakes at dawn on a clear day and can see Plymouth. How close to the coastline would she need to be in order to see the land and how long of the journey would remain at this stage given that conditions are good?
Visibility of land would be in the 20 nm range, based on real-life experience as a sailor. There are no mountains in Plymouth, Massachusetts, so that is about all you would get.
An old-timey sailing ship like USS Constitution would be lucky to hit 10 kts. Since this probably isn't a heavily manned warship built for speed, 5kts or under is more likely. So the ~20 miles to land will take you four to six hours, depending on the wind conditions.
If she sees land at dawn, the ship should anchor before noon....assuming they found a good place to anchor. You don't just drop anchor anywhere, and it could take days to find a reasonable spot to anchor along the coast.