I would like to help you with your question.
I can understand how frustrated and worried you are about your daughter's weight. Unfortunately, the reality is that she is an adult and you have no control over her weight. While she does not seem to see the same body picture you do when it comes to her own weight, the truth is that only she can manage this. Is she in denial? Possibly. Does her weight bother her...apparently not.
The likely reason her physician did not take action was because eating disorders are a dangerous occurrence in our society. As long as your daughter is not bulimic, anorexic, or otherwise in a destructive relationship with food...her physician understood that attempting to push her into dieting could have negative consequences and would not be a healthy choice at this juncture.
Please understand that a 21 year old is still trying to find their place in the world. If she is okay with her weight...you need to learn to be okay with it too. Eating disorders can lead to death. Please trust that if her physician thought she was significantly overweight, he/she would have referred her to a dietician.
The best thing you can do for your daughter is to continue to build a healthy relationship that allows you to talk about every and all subjects. If she ever becomes concerned about her weight, you want her to be able to come to you and be supported. Pushing her into dieting now may close that day.
*I meant: pushing her into dieting now may close that communication.
I understand how much you want your daughter to look good and be healthy. As long as her physician is giving her the green light on her health...stand by that assessment.
My problem is she probably will not be seeing a doctor anytime soon and I'm sure she did not pick up on her BMI. I asked her what it was since she was telling me it was going to be high and was discussing it with no problem. She said it was going to be high because the yoga she has been doing made her arms and thighs bigger. I guess I'm concerned since she is in so much denial. This is not muscle this is fat.
If she is in yoga...then that's a very healthy activity and it will help her stay in good mental and physical shape.
While she may be in denial about her body size, she is not plagued by an eating disorder...and that is far, far worse. Perhaps you can find a fun way to engage her in exercise by inviting her to go on walks, swimming, gardening or other similar things. You complain about her portion size...so why not tackle this by buying smaller plates...that way there is less room on the plate. You can also cut down on sweets, unhealthy snacks, and fast food. Perhaps you could plant a small garden or even do a container garden so that she can eat fresh food off the vine?
Bringing negative attention to her weight and body size is not going to be received well and will surely backfire. Rather...if you compliment her for her fashion sense (when she wears clothes that really fit well and look good on her) and highlight how good she looks in certain colors or fabrics...you will be helping to build her self-worth. And, a strong self-worth is going to help her see and address a weight concern.