Oh- I think it depends on each situation.
It is a good idea that she attend your beginning classes- to get the idea of the way you teach,but more importantly the real question is why- does she want to teach? And ask yourself what makes a good teacher? then ask her. I have found in becoming a teacher- that it is a combination of absolutely loving the form, wanting to share, and showing up with grace and boundaries.
Good Luck*

Who's ever ready to start teaching? :-) I think if we'd had any idea at the beginning, we'd sure think twice about it!
If you help her, it's called mentoring & it's another cap for you to to wear in addition to whatever else you do now - having her in on your beginning class is a good start, esp. if you can discuss it afterwards so tell her why you did such & such. It's also worth her paying you something for.

Have others asked her to teach, or did she come up with this herself? If the latter, have her explore her motivation to teach. There could be many unconscious needs pushing her desire - hopefully she's in it for the art itself, but it could be she's thinking about making money, collecting fans; maybe sees it as another way to practise herself, etc.? Getting to the bottom of this desire can be tricky.

If you can help her understand that teaching is an actual job that you have to work at, a service you provide for others, and it's not all about the teacher & what the teacher thinks or wants -

Dear Bea,
I teach a course in how to teach, but I have also recently taken on an apprentice. She studies with me in regular class, does private classes with me and is part of my dance company, so she is actively learning at many different levels. She also attends my classes to observe how I teach and when the time is right, she will be co-teaching with me. The key is, do you WANT to teach her the things she needs to know to be an effective teacher. I think in examining your own feelings and motives, you will find many answers. For me, I am 56 years old and would like to be assured that someone will carry on my particular work in dance when I am retired. I have utmost respect for my apprentice. She cares about the dance, she cares about the students and I feel really good about working with her, and in leaving a teaching legacy in her hands. In 35 years of dance, there is only one other person that I have felt this clear about. I know that not only will she teach with integrity, but she will also bring her own vitality and thinking into the mix.
Regards,
A'isha