Told on my girlfriend to her Nutritionist after bariatric surgery about her real eating habits

A little bit of context, my girlfriend had her operation 1 year ago, and went from 260 pounds to 125 pounds. She is steady at this weight for some time now (~3 months) and her recent bloodwork and all that seems fine. I met her 7 month ago, and have been living together for about 6 months.

But...as the title suggests, I told on my girlfriends to her Nutritionist while she was in a remote call with him. She was talking about her diet, and she was lying through her teeth that she only eats healthy. I was looking at her and couldn't believe it. She knows and admits that she was lying. I know for a fact that she eats candy every day which makes up to about 60-70 grams of sugar daily at least + sodas with sugar in them.

Now, the thing is, while she was in the call, I couldn't help myself and said outloud so that the Nutritionist can hear me something along the line of "tell him about the sodas and real candy quantity that you eat every day and why you do it". The Nutritionist overheard me, and asked for more clarification. Naturally, my girlfriend confessed but the Nutritionist was disappointed to learn that my she was lying and tried to provide support on this.

After her call ended, we had a big fight and she said that I should not intervene in such matters and that I put her against the wall in front of her Nutritionist.(a bit dramatic, I know). he continued saying that it's none of my business and whatever she does with her life. But, obviously, she is not in control about her eating habit, and lying about it.

I studied psychology and worked with people all my life. I feel that I did the correct thing, since I do not feel that she can be true to her self and to her Nutritionist. As long as she provides false data about her eating habits, and the bloodwork and weight "feels" and "looks" right she will continue to abuse sugar (because it makes her feel good****il it's too late and starts gaining back weight and other complications. Moreover, she receives positive feedback when cheating. This won't stop, and I am afraid that if I would not intervene such things could go unnoticed by the proper authority (Nutritionist and Doctors).

My questions are the following:

- Did I go about this correctly by telling on her to her Nutritionist? Is this something I should not get myself involved in even if I can clearly see that she is not controlling herself?
- I know that she will resent me if do not stop doing this (telling on her) and stop trying to tell her not to eat sugar in an abusive way. I love her and I don't want us to brake up, but at the same time I don't want her to go back to where she was mentally and physically.

She is also doing therapy right now (not for this situation but this will be addressed as well) and is constantly changing and growing. There are a lot of variables here.

Any advice?
Have you had any such experiences and what is your take on it?

Thank you...