No penalty. For me it seems very straightforward:
Hassan was looking at Dibaba in front of her and trying to pass her. Hassan had to get into lane 2 or 3 if she was going to do so, because Dibaba drifted outwards as she finished. Hassan finishing outside of lane 1 had nothing to do with Muir and everything to do with Dibaba.
Hassan has a funky arm carriage so it looks worse in some pictures than it does in the video.
This especially makes sense to me in the context of the race where Hassan really looked like she had a shot at closing on Dibaba for the last couple of laps. I mean, I definitely thought she had a chance as a spectator, I'm sure she thought she had a chance as the athlete in question.