This may mean she has a congested liver, and it may take another flush for stones to start coming down. A friend of mine also had no stones and her first flush and now she is amazed at how many are pushed in her flushes..
i know it is a bit disappointing not to see stones out after having had the oil+juice, but trust me this is normal!
Your girl should have some bile mover for a week or two before flushing. Either Artichoke or Chinese Bitters tinctures are great and help move the stagnant bile, so, as a consequence her second flush ought to be a successful one.
Don´t give up! Read Mrs Chang´s website, very educational as well.