Hi Everybody, And please notice that a lady dressed in black is obscuring Lee from at least the waist down.
Optical illusion caused by shadows & what Mrs. Reese is holding in her right hand:
===> Pauline and Sarah are on the East side of the steps.
As pointed out before, your 'Pauline' is an optical illusion:
'She's' either a Jack-In-The-Box, or 'her' tiny 'face' is a film artefact, with 'her' 'hairline' a horizontal glitch that appears in only ONE frame:
And note that 'her' 'skin' is too dark compared to the skin of real people in the sunlight. Explanation: this 'face' is just the same background we see in all the other frames where 'she' doesn't appear.
**
There is absolutely no reason why Mrs. Sanders couldn't have moved across the landing (if she was indeed where she recalled having been) between the shooting and now.