Oh my gosh - my heart goes out to you. There are a ton of resources through cancer clinics - ask for help in starting the conversation... and the plan. Does your Does she have to do surgery / rads / chemo? Or, will surgery be the only treatment plan followed by careful monitoring?
The other MAJOR resource is going to be other families with kids with diagnoses similar to your daughter's. A social worker through your cancer clinic can help connect you to groups like that. By talking to other parents, you might get some good ideas about how to proceed.
I wish you the very best luck - I cannot imagine having to have this conversation with my own child.