Because the latter involves a contract. They gave Bernie money because he promised them something in return. Bernie lied and the money was lost. Both parties offered consideration, but only one party handed it over because the other party lied about it.

The woman lied to the girl, but took nothing from her. Hence, nothing was lost. In other words, no consideration was exchanged, nor was there even a promise of any consideration being exchanged. It would be like if Bernie told you he was an honest, expert investor (while being a total fraud), and then nothing happened (you didn't promise him anything and he didn't promise you anything).