User blog comment:Miskos3/Fairy Tail Episode 190: The One Who Closes the Door, Review/@comment-7418318-20140712063833/@comment-7418318-20140712125418

As Miskos said, we did get to see the arm lying on the ground, so I'm pretty sure she lost if from debris rather than a Dragon. Since Dragons eat Humans it's unlikely that a Dragon would bite the arm off and then spit it out again... or that he would only bite the arm instead of swallowing her whole.