Not bashing. I'm recommending that when looking for the stablest candidates for long-term relationships you avoid those who indulge, and assess that by looking at tendencies.
In an imperfect world - where EVERYBODY is going to tell you that he or she is and always will be faithful, he or she is and always will be drama- and headache-free, all you can really go by are people's past actions and present behaviors.
It's certainly not an on or off switch… there are plenty of degrees. A woman who's only having one or two drinks a month at a bar with girlfriends is an order of magnitude different from a woman who's getting plastered once a week in loud nightclubs in tiny dresses, for sure. And then a woman who doesn't drink at all or do girls' nights out is in a different category too. You might think of it as a continuum - and it goes both ways, of course… you can view men exactly the same way - e.g., a man who goes out clubbing and drinking hard once a week; a man who goes and has drinks at the bar with his buddies once a month; a man who doesn't patronize bars or clubs or drink at all - all in rather different categories regarding general levels of risk for relationship problems and distraction.