Why is it

Why is it that my niece only see the good in people. Her dad hit her and left marks on her. Her mom left him and hes trying to contact her and talk to my niece. She's always asking about him or says she misses him. She was around 4 at the time of the abuse now she's 6 hasn't seen him since and asks about him still. Is it because she has an innocent mind set? Or what.