Complex sentence: On the outside Lady Penelope is just another member of the British landed gentry and fashion icon, after completing her education she rejected the aristocracy's endless round of social engagements and became a secret agent.
Split into simpler sentences: On the outside Lady Penelope is just another member of the British high society and also a fashion icon. But, after completing her education, she rejected the aristocracy's endless round of social engagements and became a secret agent.