Don't know how to title this.

I'm on the board of a non-profit organization that teaches salsa classes.
We have a weekly practice day and one of the people that comes to have weekly salsa classes, let's call her Sara, has shown interest in becoming a teacher.

Sara's skill level is, without a doubt, not high enough to become the person that assists the teacher, in our organization.
Our classes always have a teacher and besides that, we have a "helper" present to help out new people, in case the material being taught, is too difficult to dive into, as a beginner.
I have with the board decided to offer to take Sara under my wing (I'm the regular "Helper").

Today I did so, and asked Sara to dance with the beginners, but without helping out as a helper, and instead observe how I do the job, and I would also give out tips to Sara on how to be a helper.

At first Sara quickly lost interest and focus on the tips I was giving her.
A bit later she started teaching as a helper, which I had to ask her not to do. She told me she felt like I was being condescending when I asked her to observe and not teach. Later she told me she had done pole dancing for two years, and a lot of the same principles apply, and that she had been dancing salsa for two years already and knew everything.
I told her it's dangerous to ever think you know everything.

So now I'm considering having a private talk with Sara, and in the most polite way, tell her what I've observed, and that she can try to become a teacher, but she will have to face that her level is not there yet, and that it will take work to get there. The tricky part is, Sara is immature in some areas, and some of these areas, she will need to work on, in order to become a teacher. I have a friendly relation with Sara, and I'm focused on doing my job, as a part of the organization.

Is it a good idea to have this meeting? How do I handle this situation well?