I don't know much about lucid dreams or what makes you lucid. It's rather fascinating that your mother said she knows it's a dream but it really doesn't matter.

Anyway the first and foremost thing to say here is that death in dreams does not represent death. It represents change. The loss of your old self, probably innocence judging by the way that Pippin acts towards you. Whatever he is like in reality as a dream symbol it's simply something dirty.