I'm making an official guess as to who Tamara is...

Crazy with that taser:

And manipulates men with false identities:

She certainly knew a lot about potion making as well as magic

AND before she took the potion she admits that she wasn’t “quite human”:

There was also the magic in a bottle hint and she sat by a fish tank. 

She manipulated August, who’s greatest desire was to be fully human (August/Ariel parallel)