Support for my teen daughter

I am so sorry that you are having to go through this, no one in their lifetime should have to experience cancer. It is an unpredictable and horrible disease. We are here for you, from all walks of life we are all going through something so similar so let us be your support system and outlet- even though we are strangers.
As for your 13 year old, she's still developing and she probably doesn't know how to handle/process the emotions she is feeling suddenly within herself. The only thing that I can think of to help would be, does her school offer counselling/some sort of therapy to their students? I know she's young and it's hard but it could be very beneficial as often school councillors are specially trained to help the younger mind. It might help her as she can openly talk to her therapist, I'm not saying she can't talk to you but from my experience I am reluctant to talk to my own mother about it as I don't want to let her know that I am suffering as much as she is. 

Another way that could help/help her understand fully what's going on is getting booklets from your local hospital about bowel cancer. It offers descriptions about what to expect, what cancer does, what treatment plans, what treatment side affects could be. I understand that you said he is too sick to receive chemo but these booklets could still help her understand. It might even be beneficial to take them to school with her to show a therapist/counsellor. Are her teachers/school aware of what's going on? Part of the anxiety about her not wanting to go to school could be when she's upset she doesn't know how to say/describe what's going on at home so if teachers are informed this will take the stress of talking about that off her. They could then possibly put some things in place for her, like if she ever gets upset in class she could go somewhere calm to calm down. This could benefit her school life, and she might want to go more.

Once again I am so sorry that you are going through this, as well as your children.
I hope things look up for you. 

Hello and welcome to the forum, i am so sorry to hear about your dad and how it is impacting your family, there is a cancer charity for patients and their family where you can drop in between 9am and 5pm, no appointment needed and talk to qualified staff, search www.maggies.org hopefully there will be one near you, take care, Eddie