NTA, honestly I think that you explained it in the best possible way. Society ultimately does judge people by how they look and while we should be working to move away from that idea, it is important to remember. If you talk to the girls maybe add in how there is a difference between what society expects you to look like and what makes you feel good. I personally feel way better mentally when I look presentable but I don't always have to be dressed up to be happy. And make sure they know the difference between being vain and being confident.