She will need to take the registration document with her as it's the first MOT. click here
"An MOT can be carried out at any time If the vehicle is tested within the calendar month prior to when the MOT is due, the test certificate will run from the date of the test to one year after the expiry date of the current certificate. For example, if the current certificate was due to expire on 1 April 2007, and the vehicle was presented on or after 2 March 2007, the certificate would run from the test date until 1 April 2008...."
The same rule would also apply when the vehicle is taken in within a calendar month of its first MOT. In this case, the vehicle owner would need to present their registration document.
If the vehicle is tested earlier than one month before its due date, the MOT will only run for twelve months.
See underneath the link on my post to: 'The same rule would also apply when the vehicle is taken in within a calendar month of its first MOT. In this case, the vehicle owner would need to present their registration document.'
I'm not sure if the reg doc is required on the actual date the vehicle is three years old. The above applies if you go for MOT before it's due, as it states.
I believe correspondence is sent from DVLA before the three years are up and this can be used at the MOT station. Then again, I seem to remember the station needed the reg doc, when my car was three, in order to verify the vehicle identification numbers actually related to that car. TC.