Were it unprecedented, then perhaps: after all, I could no more justly hold my girlfriend accountable in such an eventuality than had her beverage been deliberately contaminated by some ne'er-do-well seeking to parlay the situation (and her inexperience) to his advantage. Suffice it to say that not everyone knows their limitations and, trust being paramount in my estimation, I couldn't but take her word at face value in the first instance. Indeed, whilst the countervailing argument remains: that alcohol does not so much conjure sentiment out of thin-air as act to disinhibit dormant and repressed or otherwise underlying impulses; inhibitions are, in essence (and loathe though we may be to admit it), the only thing that prevents us from 'cheating' to begin with. As such, extenuating or otherwise adverse circumstances should, to an extent, be allowed-for.
However, I should (quite logically) find myself less charitably inclined toward someone that, having prior awareness as to their own susceptibility in that regard, undertook to imbibe copious amounts of intoxicant notwithstanding. That would be simply flagrant.