Re: the laughing vs crying. To be honest, I can't tell. If you are making your crying face, and all others can see is your cheeks and teeth, it could look like you are smiling/laughing, so as much as I hate JA, I can't say that I am sure that she was laughing in that moment. I think it's easy to project that onto her because of how much we loathe her and because of the type of person she is, but again, I just can't say without being able to see her entire face, vs just her cheeks and teeth.
I do think she was really crying, because real tears were falling, but I also don't think that that matters. It makes her look a touch better than the typical sociopath, but that can just be acting. Her ACTIONS that day, and the days following, heck even the days leading up (stealing the gun, all of he preparation and thought put into the road trip), tells me all I need to know about her. Crocodile tears or no croc tears. She needs to spend the rest of her days under lock and key because with her possessive, obsessive, stalker sociopathic personality, no one is safe with this nut on the loose.