Bess' sacrifice can be seen as noble because she is willing to give up her life for the man she loves. However, it can also be seen as pointless because it does not ultimately save him. In fact, it could be argued that Bess' sacrifice actually makes the highwayman's death more tragic.
Ultimately, whether Bess' sacrifice is noble or pointless is a matter of opinion. There is no right or wrong answer. However, it is clear that Bess' love for the highwayman is strong, and she is willing to do anything to save him.