We've actually been wrong about space for a long time (and by 'us' I mean Hollywood). Being 'cold' means losing heat, and we feel cold when the environment around us saps heat away from our bodies. Most of this heat transfer occurs as a result of conduction and convection from air particles. In space, it takes a lot longer for body heat to dissipate, since the only way it can is by expelling warm particles from our bodies.

Yeah, but it's understandable that Starfire may not have been prepared to explain that.