My AXGF would smell of alcohol for, at most, a few days after stopping. By the time the alcohol-withdrawal shakes had stopped she'd be smelling "normal".
A remaining smell of alcohol for months after (allegedly) stopping is either secret drinking or, as Ago says, something seriously wrong with their metabolism.
I find Occam's razor useful for this kind of thing - either a) a known alcoholic and one with a track record of secret drinking has resumed drinking after treatment and is lying about it, or b) with peculiar timing and despite continuing sobriety, they have developed only a few symptoms of a relatively rare medical condition that, strangely, gives the impression that they've resumed drinking.
I know which one my money's on.
Mr B.