Finishing their words/sentences is a personal thing, some people like it some people hate it. But it seems she's happy with it, but it might be worth touching base to check what she wants with regards to that anyways. I can only offer my own experience with therapy as a stutterer, which unfortunately is more of a "what not to do". But once my therapist caught wind of my stutter, it was like nothing else mattered. All the advice or support she was wanting to offer was how to fix my stutter, even after I told her I didn't think that was necessary, viable, nor what I wanted to do. But it sounds like you're doing great and she's enjoying it, so keep doing what you're doing.