Ain't a thing I don't know about drunks.
This chick is on Xanax or Aderall and, in my layman's opinion has some sort of life long neurological condition.
Probably pseudo BulBar Affect. It's inappropriate laughing or crying at often inappropriate times. Either way this incredibly mawkish and ignorant woman ain't playing with a full deck.
Could be some of that involved, I havent been around a lot of people abusing either but even if she were laughing uncontrollably due to something like that then there generally would be other symptoms.
One minute shes rebooting like a depressant and the next shes at 100 miles a minute. If she were on something then she certainly wouldnt be the first person to abuse more than one thing simultaneously or to alternate to turn different states on and off.
PBA might sound something like that but doesnt look quite like that. If a person were abusing a substance heavily or in combination with others that certainly could cause some sort of emotional dysregulation but the person experiencing it generally couldnt control all that well which emotion is being seen at any given time. That is to say, she couldnt always act goofy and silly on stage and then become Hitler when she walks off, sometimes someone other than Cacklebeast would show up on stage.
Irritating laughing, even if somewhat inappropriate at times, just isnt enough to even make guesses on. It just makes her weird, and even at that, her personality is only entirely weird to those of us in the other regions of the US.