Depending on her size (and/or preference for bagginess, if she's on the small end of their size range) and on your $$, you might want to check out Duluth Trading. Their primary advertising for women's clothes seems to be "So, you're a lipstick lumberjack". XD The quality of their clothing is very good and they have decent sales. I bought a men's flannel shirt-jacket that you can try to pry out of my toasty-warm dead hands, and a couple of henleys that are ridiculously soft.

If she'd like more menswear inspiration, look up Esther Quek and Janelle Monae. Oh, and Ruby Rose.