Simplify the following text for a Grade 7 native English-speaking person.
Original: Florence Nightingale , OM , RRC ( , historically ; 12 May 1820 â `` 13 August 1910 ) was a celebrated English nurse , writer and statistician .
Simplified: Florence Nightingale , OM ( 12 May 1820 â `` 13 August 1910 ) , was a famous English nurse .