I'm sorry, Phi, but as written it feels overpowered. So I'm gonna heckle you a little to get a better idea of what you mean. Especially regarding the science behind it.
Firstly, Level 0 means no ability; abilities start at level 1.
Secondly, why is contact with the ground important?
Thirdly, can it be any metal? That's a large portion of the periodic table.
Fourthly, how does her ability let her change the number of protons in an atom? Especially at a mere level 2, my knee-jerk reflex was "I don't want her turning carbon (people) into mercury."
Fifthly, similarly, how can it create matter from nothing? Conservation of energy and all that--unless you meant the literal air, in which case the final level is largely redundant. (Not that redundancy is a bad thing. I think powers are the same from start to finish, they just grow stronger with practice.)