Yep -- this is the woman responsible for Hailey Baldwin's ON-POINT looks on the daily ... Maeve Reilly, wearing a revealing sports bra as a top yesterday during an outing with her client. Hey, it's Alexander Wang, it works!

Hailey's looks are always on the cutting edge -- in fact she wore a black bustier with denim, Tuesday -- THE latest look for Hollywood starlets.

And the day before that, Hails was wearing biker shorts -- another of-the-moment look -- but in a zebra stripe! Breakin' ALLLL the rules, Hailey! Check out this clip of her driving hubby Justin Bieber around and then lunching at the Hotel Bel Air in Spandex. A few years ago, a person woulda been kicked out of the posh resort for wearing this!