Iirc, all clues seem to point to her having been prescribed lamictal. Mostly due to her mentioning the death rash and also "doubling" and "tripling" aka gradually increasing the dosage to a maintenance level.
I agree with the view that she's stopped taking it. I do think she took it for a bit since she did mention the dosage increases, but now it's gone quiet and she seems like normal bitchy mood swing-y Amber. Lamictal has nasty side effects. I think she either reached the point where the dosage was high enough to take effect and got wiped by the side effects. Or, my own theory which is that she stopped all contact with "the girl" aka the person who prescribed it, and thus lost access to prescribed refills. Maybe the quack said something wrong and nicked a narc nerve, maybe Amber just got too damn fat.
I don't know if being morbidly obese puts you at risk for complications with lamictal. I'm sure it would somehow. If it does, that might have led to her being taken off it.
Eitherway, she won't mention it unless she can twist it into a situation that makes her look "brave" and "badly strugleen with the mentals."