A girl, who keeps her horse at the same yard as mine, has asked me to help her with her riding.
From what she said she's watching other riders avidly and wants to learn, so I'd like to stop her going the wrong route but don't have the experience to teach.
I didn't have the experience to teach until I taught my first rider!
If you are riding according to classical principles and she can see that you are getting results and wants to ride like you, then please try to help her. It doesn't have to be in any way technical; use whatever language you are comfortable with.
she's much further away from working her horse correctly than she can be expected to realise and might lose patience and give up on lessons altogether if given a too honest opinion.
If she is genuinely ready to learn, she will accept the honestly delivered constructive criticism.
Offer her encouragement, talk to her. Let her watch you in a lesson. Explain to her that you are learning too - that we never stop learning.
Offer to ride again at the same time as her. Explain the necessity of good posture. Show her how to get a horse to increase his impulsion through the timing of the aids and to establish a contact. Once I see the face light up at the feeling of that I know the rider is hooked.
If she is showing an interest in what you are doing show, she must be recognising that what she's doing isn't working and she wants to know why it is for you. Help her to begin The Journey.