The context is this: two women are talking, with the first one (still unnamed) that asks the second girl (Himari) if her trip with her boyfriend went well. She says it was a very nice vacation and then:
陽葵の顔が、ぱーっと明るくなっていく。
Himari's face was lighting up in enthusiasm.
The second woman smiles for Himari's mood swing, but I can't understand exactly what the phrase means:
その変わり様を、彼女は現金だとでも言うように軽く笑う。
The phrase seems to mean in a literal sense something amongst the line of "She smiled for her change, as if it was cash", but I don't think that's the case. Apparently "現金" in a -na adjective can also mean "calculating/self-interested", but I'm not sure that you can construct a -そう-like phrase with "とでも言うように". Any help?