Letter of accommodation for business trip, staying with partner

[UkScientist]

Hello,

My partner, who is Indian, emigrated to the USA to take a one year job. I have already visited twice, and it happens she needs to come to the UK to present her research at a high profile conference. As such she is applying for a visit visa, with letter of invitation from the conference organisers etc. The UK government has granted her research funds to pay for the trip via a successful application to a UK government scheme (i.e. the uk government is paying for the flight, food costs etc).

The conference is near enough to me, that she will stay in my house (free of charge). As such I need to provide a "letter of accommodation" explaining I will be hosting her stay. Is it enough just to stay I will be hosting her stay or do I need to say something about myself and relationship to her? If so, would I be expected to prove we are in a relationship, even though this is not the main reason for the trip?

Thanks,

Peter