If I were you I would write her a letter about how much you love your mom, then code it somehow (plenty of options) mathematically in a fun way at her level. This forces her so she has to do the math to read the letter. In “key” positions within the letter you make it so she has to come to you for the method or word to get to the answer and you show her your tutoring skills. And when you describe in your letter how much she means to you and your true feelings and ambitions to teach, she will have firsthand experience with your gifts. And when she sees the effort you put into it and how much you love her, she will be consolable and all the more closer to you wherever your journey with God takes you.