I understand your annoyance here, but it wasn't super wise to share the recipe with your best friend if you didn't want her to use it for normal cake-related things like baking for people as gifts.
If gifting these cakes to mutual friends no longer brings you joy because you know she's doing it too, it's fine to stop. But you shouldn't let her get in the way of what sounds like a really rewarding tradition. Bake your old family recipe for the friends who don't know your recipe-stealing admirer. For everyone else, choose a new dessert. And guard that recipe with your life.
[
add
]
[
|
|
...
]