My sister wants to sell our late grandma's secret recipe to a company and I don't know how to stop her

My grandma passed away last year. She used to run a small bakery in our town for almost 30 years, and she had this one recipe for a spiced apple cake that people used to drive from other towns just to buy. She never wrote it down anywhere. She taught it to my sister and me by hand, over and over, until we both knew it by heart. It was kind of our thing with her.

Last week my sister told me a regional food company reached out to her after seeing her post the cake on social media. They want to buy the recipe, put grandma's name on the packaging, and sell it in stores. They offered her a decent amount of money, and she seems excited about it. She says grandma would have loved seeing her cake in stores everywhere.

I feel really uneasy about it. To me, that recipe wasn't just a set of ingredients, it was something private grandma trusted us with. I don't like the idea of it being mass produced in a factory with grandma's photo slapped on a box just to sell more units. My sister thinks I am being overly sentimental and says money is money.

We have not fought about it exactly, but there is tension now every time it comes up. I don't want to make this into a huge family issue, but I also don't want to just stay quiet and watch it happen if I have real concerns.

I want to explain how I feel in a way that doesn't sound like I am just trying to control her decision, since technically she can do what she wants. I just don't know how to bring it up in a way she will actually hear.