The character of Nadia is like she is selfish and She will ally herself with anybody and employ any tactic to further her own mysterious agenda which is similar to Damon. It was clear from 'I know what you did last summer' that Elena still has feelings for Stefan while Tessa is the new love interest of him. 

So my personal opinion is that Nadia should play the genuine love interest of Damon. Only that would give a balanced sheet to the casts. 

Agree anyone?