Complex sentence: Later in life she would claim that she was born on 25 December 1785, a lie she maintained to such an extent that even on her death certificate there is no certainty about her age, stating that she was "about 80 years".
Split into simpler sentences: Later in life she would claim that she was born on Dec 25,1785. She maintained this lie to such an extent that even on her death certificate there is no certainty about her age, stating that she was "about 80 years".