Is it safe and helpful for her, with no risk to me, to work with her further?

We would recommend that you disengage, simply for medical and legal reasons to not be in a chain of connection to her should something terrible happen she is pushed into. You are right in knowing there are vulnerable aspects to have it on record you'd been in communication with someone who is diagnosed as mentally ill. So you could be blamed for doing something to disturb her or hold out false promises of treatment you are not legally entitled to do, and in the course of events actually causing harm by possibly validating her symptoms the mainstream considers delusional, and thereby inflaming her circumstances and perhaps having a responsibility for a worsening of things. This is not worth taking on, given that your interacting with her will not be very productive. It would not be useless because she does need people in her life who are normal and who can keep the discussion grounded and help to not go immediately to the extremes of possibility, but that is simple persuasion in the short-term and will not change her thinking. So temporary reassurance has but limited value. The only thing that can help her is intensive divine healing being done behind the scenes. This you have launched and is ongoing. So the bottom line here is you have done all you can, other than repeat sessions to strengthen the intentions for her betterment.