This sounds like a very difficult situation, not only for your children, but for you as well. You are really brave to reach out and ask these difficult questions. Finding out your child has been abused is devastating; knowing that it was a family member who was the perpetrator makes it even more difficult. That said, it sounds like you have already taken some active steps, like calling the police and having him arrested.
Hard as it may be to hear, itís not uncommon for children to be angry with parents when they have been abusedóeven non-offending parentsóas they are struggling with their sense of safety, and issues of trust and confusion. Turning to another trusted and loved adult is also not surprising, though I am sure itís hard to watch.
One of the best things you can do to let your daughter know you are there for her is to tell her. She may very well be feeling angry and upset, but your continued presence and support are key.
Getting professional help is also very important. Trauma-focused cognitive behavioral therapy (TF-CBT) is an evidence-based treatment for children and adolescents who are exhibiting signs and symptoms of post-traumatic stress disorder. This treatment is a joint child and parent therapy where the family learns new skills to process thoughts and feelings associated with traumatic life events. It might help your family in this difficult time.
Itís also really essential that you are getting the support that you need so you can talk about your feelings and what happened with your children, and feel empowered to continue to set expectations and renew and redefine the relationship with your children. Having your own therapist will give you a place to say things that you canít say in front of your children, and get the help you need so you can be a better parent. Therapy for you may also be able to help you set more effective limits for your children.