However do not put down your girl is accomodated at your freinds house, that is not sufficiently good enough in terms of adequate accomodation.
I too share my friends 2 bedroom house with him and I pay him rent. If I had a letter from him confirming a rental agreement is in place to live at his house for x amount of time, would this be ok for the visa app, or is it just an outright definite no-no?