this is something you need to sit down and discuss with her---should have been discussed & agreed upon before beginning- some people charge by the hour- some by the project/class- it needs to be an amount that is fair to both of you- what is YOUR time worth to you? is that an amount she can afford and thinks is fair? it is something you need to sit down with her & talk about-before going too far- it's kind of 'unfair' to give classes for free-with no discussion of compensation---then suddenly expect compensation- without discussion.