Sorry I don't have a link to any research. Maybe your contact could ask her consultant for the link to the research to which he/she is referring?
I was told (about 8 weeks ago) by my oncologist that latest research shows no advantage for primary breast cancer patients to staying on AI beyond 5 years so she is switching me to Tamoxifen (for 5 years) after I've taken Letrozole for 5 years.
During the time I've been taking Letrozole (since Spring 2010) I've variously been told I'll be on it for 5 years, then 7.5, then 10 and now back to 5 years. This is by various consultants at different stages, all, according to them, in line with latest findings in the scientific community.
It seems there is quite a bit variation in the medical community and different oncologists have different opinions and I don't think it make any difference whether they are wearing a private or an NHS hat.
Personally because of the potential deleterious effect on bone density, I would prefer not to take AI for any longer than it has been proved to be beneficial. I will however, be asking for regular reviews post 5 years so that if recommendations change I will be treated in accordance with the latest.