So…did Jen commit suicide or not? I thought that considering what we've seen her do before (flying, etc.), she probably didn't actually die. Lo's smile after she jumps should also be noted. I've seen multiple interpretations of this scene, but I prefer to think that she lived because it would otherwise be the biggest Downer Ending ever.
This seems to be a point that Ang Lee has left deliberately vague in the film, and has spawned multiple interpretations. The most convincing explanation this troper has come across (see http://www.brightlightsfilm.com/33/crouchingtiger.php ) is that Jen, in her quest to be a free warrior, has seen that this path has not brought happiness to the other women fighters - neither to unscrupulous Jade Fox, nor the honourable Shu Lien. She realises that no matter how much Lo loves her, and even if he were to marry her and cherish her, true and honourable freedom cannot exist for her as long as she is a woman in that world. The secret wish she makes before she jumps off the mountain is to be reborn as a man - or perhaps as a woman who can truly be free.
Considering how wobbly it is, would the Green Destiny even be remotely effective in a real fight?