Oswald in the doorway: the blog of the Oswald Innocence Campaign, by Ralph Cinque

When did Carolyn Arnold see Oswald? 

The situation about her is rather dicey. The claim that she said that she saw Oswald in the 2nd floor lunch room at 12:25 came from an interview she did with Earl Golz in 1978. 

http://jfk.hood.edu/Collection/Weisberg%20Subject%20Index%20Files/B%20Disk/Bronson%20Charles/Item%2027.pdf

And it was depicted in Oliver Stone's JFK movie. 

At the time of the assassination, she apparently said nothing about seeing Oswald in the lunch room. This is her FBI statement of November 30 in which she said she saw Oswald between the double doors at 12:15:

http://www.maryferrell.org/mffweb/archive/viewer/showDoc.do?absPageId=328802

And this is her FBI statement of March 24, 1964 in which she denied seeing Oswald at all at the time of the assassination.

http://www.maryferrell.org/mffweb/archive/viewer/showDoc.do?docId=11104&relPageId=8

So, in fact, I have to admit that there is doubt about if and when Carolyn Arnold saw Oswald prior to the assassination. There is definitely uncertainty. But, if we go with her very first statement as being the most likely to be accurate, it means that she saw him between the double doors and not in the lunch room. Although that statement says that it was at 12:15,  it has been suggested that the FBI changed the time from 12:25 to 12:15 to allow Oswald enough time to get up to the 6th floor.