My friend did NOT have a history of mental illness. I think her dad may have had a little OCD, but nothing else that was obvious to me. I haven't followed up with her to ask her these, but this is what I think is true:
She was not on other drugs at all as far as I know.
I don't think she'd ever done psychedelics before.
I don't know too many details of the environment she did it in, but it was with an apparently-experienced shaman I think recommended by her yoga teacher friend. It was the yoga teacher who recommended to her that she try it. All that she knew, she likely heard from this friend who had done it before.
She is a Buddhist, but I don't know what her intentions were.
I don't know anything about the shaman.
I know that it was a medical doctor good friend of hers that committed her to the psych ward afterwords, so she really needed it.