She gains her memories back when she eats Chihiro's heart.
She's also physically strong, since her body is no longer restrained by her brain as a result of her death.
(There are several 'governors' in the brain and body which limits action to prevent moving faster and stronger than the flesh can endure.
Rea is the heroine title character of the story who steals and drinks a zombie potion made by Chihiro in an attempt to commit suicide because of years of abuse by her father.
Although he hadn't had sex with her (although it might have been leading up to that) he had touched her in a manner that made her uncomfortable, took nude pictures of her on her birthday "to note her growth", had her watched and photographed constantly, fired any maid who acted 'inappropriately' (like letting Rea play with a stray cat), and he forced the family of the one friend she had confided in about his behavior to move away.
Chihiro enjoys seeing Rea dressed as a Bunny Girl or a Nurse.