I think Sciona previously was convinced she was the most dangerous thing around. Now that she's been up directly against supers and whatever Vale is and had that illusion broken, perhaps she'll be less likely to casually destroy everybody who is willing to work with her.. then again, maybe she just has Compulsive Backstabbing Disorder.
Thats clearly not the case. Something cut the head off her.
She already knew she wasnt invincible.

There's still something terribly off about an invasion plan that involves using a pathway that can be shut off permanently and irrevocably from the defending side.

Sciona literally rigged the portal to blow and close.

If the Alari were not destroyed, the strike team only needed to regroup, fly back, and blast the mountain.
There is something terribly scary about an invasion that leads the enemy army directly into the heartland of your nation.
And that its access point can be blown off by a single focused strike means less if that point is suddenly in the middle of the enemy army.
We have seen how brutal alien tech are. Its not impossible that the strike team would have died if Sciona had gotten reinforcements in time.