I think some of it is target age. If you "meet" her at 13-17~, she's probably the coolest thing ever. Smart, competent, always together, capable of handling any situation. From the perspective of 20-and-up, she's still pretty cool, and you can appreciate all that, but you also notice that she isn't really challenged, and there's never a need for her to grow or learn. Competence is great (more characters of both genders would benefit from it) but the limits of it need to be tested.