Checking character stats plus the listed heights in character creation, Theyler is 175cm tall (50 on the height slider) and the shortest option for female Elezen is 183.5cm, so a difference of only 8.5cm (about 3.5 inches). Theyler does still look relatively too tall in that screenshot, but it could be affected by their poses, and Theyler's spiky hair isn't helping the comparison either.

I couldn't find the Lakeland Elezen NPC in the list of new NPCs from the patch (does she have a name?) but Ameliance is zero height.