Spouse visa Extension - Letter from relative

[HSBilling]

Hi,

Just going through the application, the checklist mentions that I need a letter from relative/friend that me and my partner lived together for the past 2 years. My mum wrote a letter to give permission for us to stay like in the initial visa , would it be acceptable for her to write a line in the same letter to confirm that we have lived together for 2 years since my partner entered this country or would she have to write a separate letter?
Thanks.