she wants the best for her school and to create a difference in the area by teaching them more about reality of life than just books. She also asked how much will she pay for the class and I told her that its a voluntary service.
Way to go OP!
She just made the best decision when she said she wants to make a difference in terms of education.
We can read books about Bitcoin, but it's totally different when someone with actual experience long enough to teach these students what and how Bitcoin works.
You could've offered your rate easily but choose not to, such an amazing role model. This could be your stepping stone in the path of teaching students about cryptocurrency and Bitcoin.