I was abused by my uncle as a young girl, and although I do not have any sort of relationship with him now, my mom is still very close to him. He was her favorite brother and they were very close. It bothers me that she can still maintain a relationship with him, however it is her decision. She feels that he is a sex addict, and the addiction took over him. Almost like he was having an out of body experience when he was slipping into my bed at night.
Everyone has their own way of dealing with difficult situations, some dive into it full steam and work through it, and some deny. My mom is in denial, and I am diving.
Some people may keep a relationship with their abuser (if they are a family member) in order to minimize any trauma the rest of the family may feel. I know it was very difficult for me to see the pain and anger in my siblings, at times I wish I had just kept my mouth shut.
To make a very long story longer :-) Everyone deals differently. To some individuals keeping a relationship with their abuser seems obsurd, and others, it is their therapy.
Hope this helps

Carpe diem!