Just throwing this in here...
If HP took the photos and if she knew Karlie was about to "do a runner" with the cash, is it possible that HP HAS been keeping the pretence of Karlie being active around SA and the eastern states by various means (phone calls, Centrelink visit, bank visit, ATM transactions etc) not in order to cover up a murder, but in order to protect Karlie from the person/people who wanted their money back?
Maybe HP genuinely didn't know Karlie was dead.
Maybe she just knew Karlie did not want to be found and accepted that it was too dangerous for Karlie to ever contact her again.
Could this be why she was questioned by the police at such lengths but not charged with anything?