If this were the case I would leave her alone. I should've specified - the bad experience she had with prescriptions was for a completely unrelated physical and temporary ailment, and her toying with the idea of her having ADD was as serious as one spontaneously wondering if they were an earthworm in their past life.

At this point, she is becoming destructive to herself and those around her (seriously damaging relationships and unable to support herself), so while I do want to respect her decisions (I've had my own problems with people not respecting mine, especially with mental health), if she were an untreated alcoholic abusing herself and others that decided she wanted to keep drinking profusely every night, I don't feel it would be particularly ethical to "respect" that decision.

Still, this isn't to say I don't appreciate your feedback - if crap is just too complex for me or anyone to ascertain reason on without worse damage, then so be it.