Non EU partner due to join non EU tenant for a month – What should I and agent do?

I have had a tenant in my property for six months who arrived in the U.K from outside the EU to take up a new job. The original intention was that his partner, from the same continent, would join him after six months and they would live in my property together for some years.

Plans change before she arrived and she decided that my property was too far from where she had managed to secure a job, so my tenant will take up his break clause in March and move out.

The original idea was that my tenant’s partner would be referenced on arrival and a new tenancy agreement drawn up . . . . . At a cost to the tenant. The NEW plans will involve her renting her own property closer to her job and my tenant joining her once his break clause has been enacted. However, in the meantime, she will live with him in my property and he does not want to pay the agents referencing fees for her.

How does this affect my need for Right to Rent checks? Will I be in breach of this law, or will she just be staying with a friend during the four to six weeks it may take her to find and move into a suitable property? Can I refuse to let her live in my property, as she was not identified to me at the start of the tenancy?

Any help or advice welcome.

Dave