Once Stature was at eye-level with the mythological beast she realized that she wasn't sure what she was going to do with it. Distract it, probably, because she didn't think she was going to do any real damage against those scales, and its teeth and the whole fire breath thing had some real potential for causing pain. Whatever Stature did, it was gonna hurt, but at least keeping the dragon occupied would earn some time for people to get out of the way and response teams to get here (at which point, if she wasn't down or dead, she could shrink away unnoticed and stay free of S.H.I.E.L.D. prison another day). Maybe that was all just wishful thinking, but she had to try.
Trying, as it turned out, was shouting, "Hey!" to get the dragon's attention and, only as it turned, did she notice someone was riding on its back. She was too busy watching its sharp teeth and its mouth for any sign of fiery halitosis to worry about a dude riding a dragon. As soon as the thing was looking at her she rushed forward and swung as hard as she could to land a punch on its nose. For all the good that would actually do.