her right hand, like a normal person. It's pretty surprising isn't it?
Her other left hand is being covered up bt the mug so it looks like both of them are fused togther somehow. But what's I'm more interested in is What is she looking at.
her right hand, what it looks like she's doing is crossing her arms while using the mouse... Unless the artist made the mistake of drawing her left hand with the thumb on the wrong side.