Complex sentence: Out of 300 applicants for a RADA scholarship, she got down to the last three but was not selected, so she did a three-year course on teaching at the Guildhall School of Music and Drama.
Split into simpler sentences: Out of 300 applicants for a RADA scholarship, she got down to the last three but was not selected. So she did a three-year course on teaching at the Guildhall School of Music and Drama.