This right is applied per entity. If I send it to the company A, company B doesn't execute it unless they're a subsidiary of A (or A is their data controller)

This right is applied per entity. If I send it to the company A, company B doesn't execute it unless they're a subsidiary of A (or A is their data controller) and my request was carefully crafted. In the scenario you painted, that would mean that my _former_ friend has issued their request to me. In that case? Fair. Poof if that's their wish. Otherwise? How do you imagine it work?