A "masseuse" is a woman whose job involves giving people massages. When "in-house" or "house" is added as an adjective in front of the name of a job or occupation, it means that the person is the sole employee of that company. Thus, we can see that Fiona is the private masseuse of the company. Ex: I'm the in-house lawyer of the company. Ex: The company has great benefits. They even have an in-house therapist.