Ok, I've watched this a dozen times now, and I have a theory about what's going on. When the guard came over to her, she was pointing under the table, but it didn't look like she was motioning towards the floor, it was higher. I bet there is a board or some protrusion under the table that is bothering her. I used to have a keyboard tray mounted under my desk at work, but darn it if I didn't bang my knee on the danged thing a hundred times a day. I had it taken out. I felt a little silly about asking them to remove it, since I'm the one who kept hitting it.
I think she wanted to move, or have something done about the table (or her chair... get to that in a minute). This prompts the JB "child" comment, and then her offering to trade places with him. She motions to her spot in a way that says, "well if it's so trivial, why don't you sit here then?" So, I'm pretty sure the issue is with her chair or the table, and it being uncomfortable for her.
My second theory is... she making it all up because she wants a big girl chair like the lawyers have. The difference in the appearance of JB's seat and hers is very noticeable. In her mind, she believes she is an attorney, why not have a chair like them too? I bet she contrived this whole "uncomfortable" scenario so she could move into one of the big chairs. JB knows what she's doing and why, hence the "child" comment.
I think she moved to another spot (away from him) show him that it really was uncomfortable for her there and in true ICA fashion, she'll stick with the lie to the bitter end, even if it never got her what she wanted (the big chair). which is why she's still sitting there 3 days later gazing all forlornly at JB wondering why he isn't begging her to return to his side.
