The moment
Begin with a scene she will recognize: the first time she slowed the table down, the phrase she uses when everyone is stuck, or the night she made a new player feel capable.
A useful detail
Keep the note short enough to be true. One specific memory and one honest thank-you are plenty.
Keep it human
A card is lovely, but a text after a good lesson counts too. The point is that she knows her effort landed.
Let the person be the point.
A gift is optional; a sales link never replaces a useful gesture.