I don't think that Hydaelyn putting so much on the WoL isn't a thing she has really wanted as much as the only option she had left. She realised she was on the point of losing and decided to play a trump card. It cost her a lot but it as a play that it appears her enemies underestimated and it got away from them. I don't think Hydaelyn has placed everything on the WoL but we are effectively a cross between the king piece and the queen on her chessboard. We are the strongest but also the most crucial part of her remaining play.

TLR - When your facing disaster anyway a desperate play is better than an ineffective play or no play at all.