Dunno how MC maxed out his magic power at birth already.
Literally gifted by god.
She didn't give him a potential of 1002, but a direct maxed out 1002/1002.
Which is the very lowest end of 4-digit power level, so this new girl is already stronger than him (even her current score has two leading zeroes), at the very least by one point, and maybe by several thousands. Though, given her panicked appearance, she might not known how to use her power, or she's sealed in a different way than the totally-not-reincarnated-demon-lord was.
By her eyes, she's likely another non-human species, so maybe she's stuck in human form and unable to use her full power.
Or she's an ancient humanoid species, with the power of ancient magic users, but not their knowledge.
Or another reincarnated individual with a gift from this clumsy goddess... who remembered to give her an attribute this time.