Complex sentence: Her senior breakthrough came in 1990 when she finished second at the AAAs National Championships in 57.43, behind Gowry Retchakan's 57.14, to earn selection for the European Championships in Split, where she ran 56.84 in her heat to reach the semi-finals.
Split into simpler sentences: Her senior breakthrough came in 1990 when she finished second at the AAAs National Championships in 57.43, behind Gowry Retchakan's 57.14. This performance earned her selection for the European Championships in Split, where she ran 56.84 in her heat to reach the semi-finals.