Does Valen have any party banter or any conversations with the PC over the course of SoA? By Valen, I mean the Valen you get in the mod. NPC Party Valen.

Not really. She does speak to a lot of other people(NPCs outside your party) and sometimes causes the party to choose an evil path, so your rep will definitely be bad with her around.

A really entertaining NPC though, and a must if you fancy being shown what the 'chaotic' in 'chaotic evil' means ;) But she will get extremely powerful, so if you're a purist then it might not be for you, although I understand her vampiric progression has been slowed a bit in the latest release.