Breaking through Lucina's serious facade is easier said than done, as she has a hard time accepting her feminine side, let alone showing it to others. But taking the time to earn her trust is a far safer method of getting her to accept a binding, especially since she secretly enjoys it and tries to not let anyone else know that either. So long as she is tied securely enough to allow the situation to present an effective escape challenge, she will not complain too much. Her legs are her weak spot while her hair is her nicest physical feature, thus focus on outfits, binds, and gags that emphasize them over everything else. If her feminine side manages to emerge and she's treated well, she won't seek revenge.