I'd look into starting the mushroom business as a separate legal entity. This way it can be run as a business and you can have a contract that dictates who owns what share of the business and how profits are allocated and how decisions are made.
There's no way you can keep her from learning, but this might protect you from her trying to push you out and operating under her own brand too soon. Best case may be that the business grows and she buys you out. You take the money and compete...
Get an attorney.
-spence
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