Cosmetics are really affordable there, look for brands like sekkisei, shiseido and those type.
And, if she likes snacks (which girl dont like?), those japanese snacks (senbei etc) can get for a big bag at those whole sale, but same quality. and there is also different pocky and kit kat flavors we cannot get here in M'sia.
Also, go find a shrine/temple, and get her omamori, is like the safety charm/talisman, got many kinds, for relationship, for friendship, for studies, for good luck etc.
And, can get those small deco stuff, even tho not daily usage, but deco in house is also consider usage.

I'm also a girl who don't like those unusable stuff like kimono, slippers n stuff, so i hope I helped you with my comments.

Last trip to Japan we also bought lots of manga back, and lovely deco stuff from Japanese specialty store, and the above things I mentioned.. ^^
Added on September 25, 2012, 2:27 pmBtw if she is into anime or anything like one piece, in Japan they are a rage selling stuff like limited edition Chopper key chains, it's only certain design in certain location. Like limited to Kyoto edition you can't find in Tokyo etc.
Hello kitty also got, but you got to find.
Or u travel to places, get those places' magnet for her, like osaka castle got their own magnets, tokyo tower too.. or get her a gashapon, those cute type key chain, quality is high there, cannot compare to our gashapon here.