Complex sentence: Tierney and her mother soon left Spain and began travelling extensively around Europe, during which she was briefly enrolled as a boarder at Aiglon College in Villars-sur-Ollon, Switzerland.
Split into simpler sentences: Tierney and her mother soon left Spain and began travelling extensively around Europe. During this time, she was briefly enrolled as a boarder at Aiglon College in Villars-sur-Ollon, Switzerland.