If you have confirmed her suspicions, the next step may be for her to ask her father the same question she had asked you (when he gets back)
You would really want to remain objective in this. It is something you're dealing with and she should not be exposed to your feelings about this.
The facts may be listed (of what you know) You have told her that you and her father were not getting along. She is old enough to deduce a lot of what is taking place. You can let her know that you have been willing to address this issue with her dad as long as he is wiling to do so.
If there are details that you do not know for certain, let her know. Be honest. Sooner or later she would witness the family dynamics and make her own decision as to what to feel or say.
When her father returns, she could initiate the conversation with him. She can ask him his side of the story (the reason for him not living at home) With time, her anger may decrease. Let her know that being angry may not change the situation and that by experiencing this anger, she would most likely hurt herself.