She was a hero in the war of 1812 because she helped the wounded soldiers who had walked 14 kilometers (aprox 23 km) on a hot July day. She also provided them with food and water, and she helped rather than fleeing from the battle. This is why she's a hero.
"War of 1812" is the name of the war fought between the U.S. and the U.K. from 1812 to 1815. (The British know the war as the "American War of 1812" since they had another war going on at the same time.)
The War of 1812 lead to the building of more factories in the North. The North supported tariffs on their goods to help their businesses and the South did not think it was fair because they had to pay more for goods.