1. If you kill Nere before interacting with Philomeen when you get to her she just stands there looking away and you cannot talk to her. You can however pickpocket both the vial and barrel of rune-powder with failures eliciting no reaction from her.
Agreed, and you can even kill her. But when I tried to create a save in order to report this bug to Larian, when I reloaded it she was no longer there. I suspect she'd vanish on a long rest as well.