It would be rude, because you seem like you are trying to represent a real problem by subtle insults.
I believe that the best thing you can do is to say that you have an interest in your own health and physical shape and that you would like her to be a part of it.
Just as people can work on their emotional assets to better suit each other, physical being can also be worked on.
Just say something man. If you use your plan to plant the seed in her head, then it will be growing in both of your heads and yet you haven't actually spoken to each other about it.
Be sure to be nice, and relate to yourself. Again, I reiterate, mention your interest in working on your own body and tell her that it is a valuable trait to you that you would like to share with her.
If you approach people reasonably and explain how it relates to yourself when you criticize them, then you have truly mastered constructive criticism.
You don't deserve to have this in the back of your head bothering you, and neither does she (she will if you cause her to feel negatively about her body by admiring other women in a highly intentional way).
Good luck
This post was edited by ringo794 on Jun 11 2016 01:37pm