I have top laned as her a couple times. I tend to do at least acceptably, though sometimes I get zoned pretty hard in lane
I also have been running Flash/Ignite (Flash/Smite when jungling), but given her mobility Heal might be a good call.
I'm learning jungling now, though, and I seem to be okay at it with Riven. Not good by any means (I tend to be bad at resource management and either end up too low on health or simply miss with the early ganks), but I'm picking it up. Roaming Rivens are fun!
Also things I need to work on: SOME ITEMS HAVE ACTIVES
THEY ARE RARELY WORTH BUYING IF YOU DON'T USE SAID ACTIVES
STOP FORGETTING ABOUT THEM YOU DERP