If it was one-on-one, sure. The problem is it wouldn't be. It would be one-on-fleet, so Maxima would have to maxuber-tank to take the amassed fire without getting vaporized. Sydney can shield and cut loose with the blasting, or shield and fly at multiples of the speed of sound, or shield and set up a teleport. Max isn't as agile in the powers department once you get to things working on her level, because she can only do one thing really well at a time. Halo always has two options.

Plus, any ships not engaging those two can be, y'know, carrying on with the conquest of the planet.