I'd get an outside teacher just so it's no a family member situation between student and teacher. You could still help her along anyway though, it just wouldn't be a parent teaching to a student/child. I'm not sure how to phrase it -- It's more like a respect/distance issue.
You learn a lot about yourself and your child doing this sort of thing. Years ago, my son at five used to sit next to me and absorb a lot from me with a little help. As he got older I sent him to a teacher. Now, many years later ( decades) I teach both his youngest son, who is 6 and his oldest daughter who is 13. It depends on the relationship and if a parent can put on the shelf being a parent or in my case a grand parent. Because you need to be the teacher not the parent in this case. At least for that period of time. That may sound obvious but I have to tell you it probably isn't for everyone !
But that's like saying you don't want to teach your child how to ride a bike because you want to keep your distance... from your own child.
We discussed this exact topic a week ago. I asked her a year ago if she had any interest in learning and she said no. The past few months she’s been sitting with me at the piano while I’m playing, asking about the music, commenting on the ones she likes best. When she asked if I would teach her, we talked about my role as a teacher versus her mom. And that for the duration of the lesson she would have to listen to my instructions and be respectful just like she does her teachers at school and her karate teachers. The biggest concern I can see coming up initially is going to be having uninterrupted time since the classroom is the home. My piano is in the livingroom. Worse case, if it's a disaster, then I have a great friend that is a piano teacher. She has offered to teach her.
Thanks you all for your encouragement. Comments are very helpful. Also want to ask about using iPad and the Steinway APP "Etude." By the way, we do have a Steinway baby grand "S" and it is (still) in grandparents' living room. The other set of grandparents lives a half-hour walk away and they have a (different brand) more blond color baby grand (from the great-grand mother, now deceased).