I didn't notice it before you're right. Thara looks like she has a larger cup size here than Kara, and even the way Lois and Lana are drawn is more "adult". Compare this to how Churchill and Benes drew Supergirl's chest or how it looks in Robinson's Don't Cry for Justice, Argentina.
There are a few teen females who usually get drawn consistently physique-wise. Stargirl comes to mind. But mostly it's rare because artists seem to forget that not every super-heroine (particularly teenagers) is supposed to look like or can look like PowerGirl