Her Diva behaviour might be mental illness

If this is the case then it is tough to tolerate the behaviour during work time. Producers, directors, co-stars have obviously tried to be understanding and pretend it is not going on, but sometimes the mental illness increases if the person is not given the reaction they seek.

The increase eventually rises too much and everybody has a breaking point where their tolerance ends.

End of the day it is up to the ill person to admit to themselves they are ill and get treatment. They will have heard many point out they should seek help. At some point you you have to move on with the knowledge you did what you could to help.