I Love Strong Female Characters

I decided to watch Nana yesterday because that one musician character looked so badass cool. At first, the actress played this role even better than I expected. Then it turned into a real cringe disaster. What is the point of building a strong character and then turn it into just another confused girl who needs to be told what to do?

Expectations:

[youtube=https://www.youtube.com/watch?v=EWppZbbQFMo]

Reality:

[youtube=https://www.youtube.com/watch?v=HsFO9jr9XFU]

I mean, it's a nice song but she looks like a puppy besides Syoko from G-Schmitt. You would expect different stage performance from the character who acts so tough.