No Common Sense Heroine

This heroine is ignorant of the ways of the world.
Stuff that should be common knowledge, such as operating common household appliances, isn't in her brain.

The reason behind the ignorance is various. Common reasons include:
A rich ojousama raised in isolation.
An alien.
A time traveler from the past or future.
A person from another dimension.
etc.

Check the Wikipedia entry for experience for details.