So she not only knows everything, makes deals with super-villains on her lonesome but can save the lives of other Reeds when her dad could not?

Well, so far as Reed knew when he left them, they didn't seem to need any saving: he helped the Council to see off the original Celestial attack, and it looked like the battle was pretty much over by that point. Val just happened to show up after things had taken a turn for the worse, so the Reeds were able to use the portal she'd come through to escape.