The answer is simple but this will require some changes: expansion.
Considering the logistics in the other answers, long-term delivery is too difficult without special preservation methods (drying or fermentation) to be an option. Even over short term distances, bean curd "gets degraded by mechanical vibrations" (emphasis mine, quote PcMan) and does not travel well (even refrigerated, tofu only lasts 3 to 5 days).
To put it frankly, Grandma may be incredibly selfish, but I'm willing to bet she ain't dumb enough to ignore the writing on the wall. Grandma will have to test family members for worthiness, have those who passed pledge their very souls to the cause of the Westerford Heritage Bean Curd (read: swear them to secrecy on PAIN OF DEATH), tell them the recipe, and then have them settle in other nearby villages, where they will make and sell her special bean curd. Y'know, like any family-recipe obsessed, slightly unhinged grandma would do if she possessed vision.
This culinary cult, this savory secret combination, will create a 'cultlinary' franchise like the world has never known. Passed down and expanding through the generations through Grandma's wise method, this ever-widening web of bean curd stalls will not only spread, but evolve (like any "good" disease) until your world ends up with a beloved (and global) franchise named "Curdonald's."
Tasty idea, right?