the register of our interactions in the office

[Coffee Break]

I read this expression, "the register of our interactions in the office", but am finding it difficult to understand it. Could you please let me know what it means? Here is the excerpt:

She nodded. And you enjoy the work?

It’s not without complication, I said, and I thought of the former president. The other interpreters had taken to calling me his favorite; it was and it was not a joke. I’d realized that to the others it was a matter of recognition and even distinction, being requested by the accused in this fashion. That such attention could be considered desirable was troubling, it changed the way I saw my colleagues, the register of our interactions in the office, the small talk we made over lunch.

- Katie Kitamura, Intimacies, Chapter 11

This is a novel published in 2021 in the United States of America. The protagonist is an interpreter working at the International Criminal Court at The Hague. Now she is thinking back to her work during her conversation with her friend.

In this part, I understand that it changed (1) the way, (2) the register, and (3) the small talk (I hope my understanding is correct ) , but I wonder what "register" means in particular.
Would that be related to the formality level of language, perhaps...? Or, a voice range, perhaps? (Though these are just my guesses. )

 

[Tarheel]

Yes, the formality level. I'm guessing that his interactions with his colleagues became less casual and more formal.

 

[Coffee Break]

Dear Tarheel,

Thank you very much for the explanation.
Oh, so she was troubled that such attention was considered desirable, so she became more formal and unattached to her colleagues in her language, creating a wider distance between her and her colleagues.
I truly appreciate your help.