No, that's just backmeat. If it was an arm we should see her hand at her side or on her ass.
I'm with the other two on this one, that bumpy ridge going down her left side is her arm. This kink isn't my thing, but I'm somehow very familiar with it. The arms are bound tightly at the sides, or behind the back, in either case bound completely straight, forcing the individual to balance and support themselves entirely with their legs. The fact you can't clearly see her hands isn't enough for me to say she's got no arms here.
You can also clearly see that bumpy part has an outline separating it from everything else. That wouldn't be there if that was her side and not her arm. I guess you could argue that line is a seem, but it stops at her waist and doesn't continue down her leg.
You can also clearly see that bumpy part has an outline separating it from everything else. That wouldn't be there if that was her side and not her arm. I guess you could argue that line is a seem, but it stops at her waist and doesn't continue down her leg.
One problem with that; the outlined area fits way too flush with the rest of her torso. Unless her arm was just skin, it should be sticking out more. Also the way the line is curvy along the torso but straight at the waist suggests it's not from an arm. If it was it'd be the other way around, straight for the torso, with a curve at the waist as the hand would be wider than the arm.
