Point to Vanora for displaying some level of ethics that makes me root for her. Logically, she should use Saphira as a hostage - Saphira is a vile individual and little else is likely to stop Eragon from tearing out Vanora's heart but this immediate rejection of doing something cruel is good to see.

We all know that if Eragon was in her place, holding the Eldunari of an enemy dragon, he'd smash it without a moment's consideration. Probably in front of the victim for added sadism.