You could also see if some friends or roomates or a sibling or something can make fake complaints. Not anything drastic. Just tell them what Hamantha does over a couple beers, and see if they are able to relay that information back to your boss. You could also make a Yelp review, making sure to describe "that rude cashier with the [whatever hair she has, or some other descriptor] who never makes my coffee right. I don't know why, because I notice she has been working there longer than other people. She is really slow too. It always takes at least twice as long when I'm stuck having her make my coffee." Try not to bring her weight into it, unless it's something like "I don't want to say anything about her size, but the last time I was in, her stomach rubbed up against the milk jug. It made me feel really uncomfortable!"