I've never understood why we seem so adamant about forcing children to spend time with people no right minded adult would. There is no relationship to preserve when it comes to active addicts. Their relationship is with their DOC. If he gets sober and wants to have a relationship with her, the onus will be on him to make amends and demonstrate his sincerity through his actions.
She is old enough to see that he is nowhere near this. She has set a boundary that many of us adults here still struggle with. Good for her!!! She is a strong child, but still a child and support is the most precious gift you can give. Many prayers for you all!