Did Ashley actually buy the drink herself or did Ruby buy it for her? The way Mary Margaret told her to “pace yourself” sounded like she was warning her not to go overboard and get blind drunk perhaps because she was underage and MM didn’t want to be a wet blanket and put dampeners on the Girls night out. As for where they are drinking, is it Granny’s or somewhere else? Either way, Ruby probably got the bar tender to turn a blind eye by flirting a little.