It is good for her to do stretches and practice with you. However limit back hyperextension and neck hyperextension which can put too much tension on the spinal cord.

In spite of the controversy, in my humble opinion, yoga is beneficial for children. It enhances confidence,enhances physical flexibility and promotes physical strength. Exploring and learning in a fun, safe and playful way is the way to go.There is no reason why your child can not join you in yoga in a playful way and get not only health benefits but also have fun doing it. I don’t believe it will cause any short or long term harm to the child.

Certain poses in yoga can harm children growing bones by putting stress on them.

Yoga is healthier than any exercise. It's self sustainable and automatically correct.

No, I think yoga for kids is great! Go for it. As long as they have a teacher trained in working with kids, it should be fantastic. Any exercise using your body weight is totally fine.

I am not aware of any specific reason why a child couldn't do yoga.