Yeah, I've been somewhat of a closet ShadAmy fan since SA2 actually.

I mean, in my head, I can see;

As Amy matures she realizes that Sonic is never really going to settle down or fall for her the way she dreams, to in love with his freedom. As a result she begins to lean toward Shadow, but in a sutle more less crazed fangirl way.

Shadow however remains nonchalunt and quiet-but-at least he 'remains'.