Complex sentence: Mathilde decides to go with the nun to her convent where she is taken to a young woman who is in labour that the nuns tell her is a woman who has been cast out by her family for getting pregnant out of wedlock.
Split into simpler sentences: Mathilde decides to go with the nun to her convent, where she is taken to a young woman who is in labour. The nuns tell her the woman has been cast out by her family for getting pregnant out of wedlock.