I agree with what's said - it would be a very bad move, and you have no right to do this. If your fianceé wants help with writing her own letter, then let her do it - but it's the agency which she needs to write to, not the company where she's placed, to ask them to find her something better since she's making no progress in her current role. If I were her I would also write direct to the HR manager asking why her application for permanent employment is going unacknowledged - her application may have been mislaid so it is always worth following up. Whatever you do, the approach has got to come from her not you - if you interfere, you will only make things more difficult for your girlfriend.