I'm just going to assume she was repeatedly told to drop the gun and didn't. Guns can change direction pretty fast(shocker) and if she's already suicidal and the police are there, she might be thinking blaze o' glory.
Faaaaaaaair.
Plus they had a negotiator try to talk her down for thirty minutes
Thirty minutes is nothing, most standoffs last hours. Those cops not only failed to protect that woman, they killed her.
but she was going to kill her self?
No, she said she was going to. That does not mean she actually would have.