If you intend to teach English to anyone, formally or informally, it's important to make sure that your own standard of English is up to scratch. Please look at the amendments I have made to your post above. It is particularly important to use correct written English on this forum because learners will read your posts, see that you are a native English speaker and will assume that you have written everything correctly.
I have moved your post to the Teaching English section of the forum, which is more appropriate for it.
The first thing you need to do is try to find out what your potential student's level of English is now. Arrange a short conversation class with her, chat casually and informally but take note of how good her comprehension is and what kinds of grammatical mistakes she tends to make.