This is the 4143rd most frequent French word.
courageuse
Brave; courageous (feminine form).
The adjective "courageuse" is used here to describe a feminine subject and expresses the quality of bravery.
Elle est très courageuse face aux défis.
She is very brave when facing challenges.
The word "courageuse" modifies "sa sœur," indicating the subject is feminine and shows her characteristic of bravery.
Il a dit que sa sœur est courageuse.
He said that his sister is brave.
Though "courageuse" itself is not used here, "courageux" appears, which is the masculine form of the adjective; "courageuse" would be used if the act were explicitly associated with a feminine noun.