Okay.... I love the Coco, so I will take a stab (yes, that was a pun)
There is only circumstantial evidence linking JA to the gun and no evidence at all that she brought a knife.
There are records of countless phone calls from Travis to JA and we don't know what he said on those calls.
JA has not shown a propensity for violence toward other boyfriends.
Seriously, the girl is ill and emotionally stunted- could be indicative of real mental illness or drug addiction and because she is also extremely narcissistic, she has covered this up. She would rather be guilty than crazy.
She just lost it after he told her to get the fuck out.
Not probable, but possible.