I don't understand why you think Met has to have control. Alice is the one who needs to react to Met's attacks. The mechanics don't matter at all (and her standard orbs do not work with gravity, they work with Dark Energy), all that matters is that she is capable of deflecting the attacks.
The problem is that she needs to put her fist in the way of the attack. If she is slow or she gets attacked from the back for example she doesn't have any defense at all. Her barrier is good only for physical attacks, not energy based. It could do nothing against Klaus' plasma for example. It could not redirect it, it could not dissipate it.
As long as Met shoots lightning in her fist, she will never take damage. If he isn't a complete idiot and try to attack her from a different angle, Alice will have to survive a level 3 with a very damaging attack and without any mitigation.