It doesn't matter if she's maybe armed and might be dangerous later, she's not dangerous right now, and so you can't shoot her.
Can't as in "are not allowed to", of course not, defend away.
Can't as in "unable to assemble a compelling argument".....yes, kinda. I would suggest you stop, get your thoughts in order, and do some research before you keep going, because right now you're doing yourself no favors.
Case in point:
That is absolutely untrue. Mere fear and "a reason" is not sufficient to claim to be acting in self defense. Legally speaking, the acceptable cause for using deadly force is in the case of imminent risk of death or serious bodily harm, or in the defense of someone else threatened with such.
In layman's terms, the only acceptable defense for drawing a weapon and using it try and kill another human being, is that if you hadn't done so you or a third party were absolutely going to die or be badly hurt. Ashley babbitt was not mere instants away from killing that officer or even in a position to do so, therefore this wasn't justified. If you think otherwise, you should present an argument to that effect.
That's the risk they take when they swear an oath to protect and serve the public, in a job they know is life threatening. If you cannot handle that risk and are primed to shoot first just in case, you should not be a cop and you should not be legally empowered to use deadly force against other people.
Of those 3 cases, only the second is clearly justified.