I don't blame her for going over there at first, but after that, when he allegedly told her that he was responsible, it was entirely her fault that she carried on partying with him. It's not Jeremy's fault that she accepted any of his invitations to party, to go for meals, to go away for weekends - that was down to her.
I agree it was her choice to stay with Bamber for 20 days. Although pressurised by a persuasive Bamber.
She was young, in love, in a state of disbelief & invited by Bamber.
You believe in her situation & at her age you would have immediately cut off from Bamber.
Luckily you have never been in her situation.