I think you guys are doing the best you can in this situation.
This is such a tragic story, and one day when your daughter is an adult she will truly understand the measures you took on her behalf.
Have you thought of counseling for her during this difficult time? Clergy and youth ministers could also be of benefit to her and your whole family.
Perhaps her school may know of additional resources available in your area.
Large medical centers have social workers, and they may be able to help guide you, and offer some age appropriate tools.
What about Hospice? They are trained in death and dying, and helping families cope, ( do they have hospice in the United Kingdom?) They may have available resources......
Sending you support.