Board Thread:Skyrim/@comment-14027812-20131228064948/@comment-190.140.9.81-20141023092242

Interestingly enough, if you manage to kill her through a mod or console exploit, Lars will send you a letter thanking you for killing her (Thanking you for killing his rival), and if you approach him about the matter, he'll simply state that he'd rather not talk about the whole thing. (Which most likely means that Braith was originally intended to be killable. Tsk tsk, Bethesda.)