Complex sentence: While living in Paris, at about the age of eighteen, Sophie decided to become a Carmelite nun, however this would be impossible, for the Carmelites, among many other religious communities, had been abolished at the beginning of the Revolution in 1790.
Split into simpler sentences: While living in Paris, at about the age of eighteen, Sophie decided to become a Carmelite nun. This would be impossible, however, for the Carmelites had, along with many other religious communities, been abolished in 1790.