My answer was "when she asks for it".
There are many things a kid should learn, and among them, a huge number are more important than programming (plus sometimes a pre-requisite for it):
- reading
- writing
- basic maths
- critical analysis
- building your own idea
- defending yourself verbally, mentally and physically
- expressing yourself
- chosing ingredients and preparing food
- proper life hygiene
- understanding the current society, the medias, the political system, etc
- learning a second language
I recall that when I was a freshman, some kids were still not be able to read out loud correctly.
Programming can come later. Way, way later.
In fact, she may even not enjoy programming at all, or even consider it.
I think the best bet is like with music. If it's something you want to share: demo a lot of it in regular life, associate it with joy, and the kid may just show an interest in it.
Then foster than.
Then setup lessons, discipline, etc.
But don't make it a requirement.