I think it's important to remember that it is the OP who is struggling to make sense of this situation - our opinions and psychological explanations won't mean much in the grander scheme of things; they're dealing with the reality as it stands and the reality is that this is still not a widely practised activity and with pretty good reason.

I think the situation would be open to further discussion if the boyfriend had been honest about this from the start - if he'd said; look this is the situation, I know it's not healthy but I value out relationship enough to be honest and I hope that with your help things can change.

But none of that has happened - instead, the boyfriend has lied about his intentions and placed a demand on someone that they in turn can't oblige due to their own integrity.

The goal is to advise the possible outcomes - given the facts presented to us by the OP this seems a mainly non negotiable situation; she either tries to convince someone of actions they don't wish to change, or she goes along with something she isn't comfortable with at the expense of her own physical and psychological safety. Neither of which, are advisable.