Morgan let out a laugh as she saw Deimos be clearly shocked by the wave; while he may have had her beaten on sheer force, it seemed she could still win some battles through strategy. While he was surprised she focused on her speed, trying to close the distance between them as much as she could while he was stopped in the wave. Really, given his form, she should have expected the shake, but she didn't: in the split second before she could force the droplets away with her magic, Morgan was hit with the water and paused just long enough to let Deimos get away.
He ran up a side street; she watched him go, trying to think in her mental map where it went; only to one place, an alley that ran along the back of the houses on the street; an idea formed.
Morgan, in a few swift movements (and a little bit of magical assistance) raised herself up onto the roof of one of the houses, waited for Deimos to come around the corner beneath. Once he was there, in place on the cobbles below she would jump, attempting to pin him down to the street and catch him there.