Refuse to answer the question. It is not Albert’s business.
Explain that she plans to retire.
Explain that competition is making the job harder for an owner/operator.
Explain her desire to travel around the world.
A buyer is often worried about why the seller is looking to sell. From the buyer’s perspective, there are good reasons (want to spend more time with grandchildren) and bad reasons (toxic waste was found under the station). Wanting to travel is a good reason to sell the station. This should not cause concern and thus, there is no reason to hide it. While claiming she wants to retire is also a good reason to sell and may seem like a harmless lie, that misdirection makes it hard for the buyer to offer Brigitte a job upon her return.