'in the course of the year' sounds good. 'Throughout' makes it sounds as though she spent the whole year at the top of the charts - rather than coming and going (sometimes in the top ten, occasionally dropping out of the top 40, but usually 'there or thereabouts').
I'm sorry you can't change the sentence though - 'in the top charts' isn't right. Maybe it's a typo for 'in the pop charts'. Otherwise it should be something like 'at the top of the charts'.