When Riley buys the first outfit for the Bar, she tells Ivy it's not her usual style. But if you compare it with what she already wears...short skirts with relatively low cut crop tops and short shorts with the same...how is that any different? She wears a pair of short shorts and a low cut crop top, when she goes to buy it, which reveals as much flesh as the new dress, so why would she say it wasn't her usual style? When she meets Wesley and Jay in the Bar for the first time, she's wearing an equally short skirt, with an even more low cut crop top, so once again , why would she say it wasn't her usual style? The dress she subsequently buys ( though very sexy) is actually longer than some of her existing skirts and less low cut than most of her tops, so that statement doesn't really make a lot of sense. And even her first outfit for college, a leather mini skirt, teamed with thigh length stiletto heeled boots, is not exactly the outfit of someone who doesn't know that she's sexy and good-looking.
From the very beginning, Riley comes across as being sexually confident. She knows she's good-looking and has no qualms about showing off her body, albeit in a not overly slutty way. So I don't know whether the Dev is putting this is in, to make us believe Riley is not as confident, as her dress sense would suggest? But if so, I'm not convinced. We know she's going to become a really naughty, slutty girl as the game develops. I think she always knew this deep down?