Ever since Elena became a vampire in the season 4 premiere, it's been mentioned and implied repeatedly(mostly by Stefan) that she's different than the person she was as a human. But how exactly is she different? She has talked about she feels things differently. The most obvious being her human feelings coupled with the fact it was Damon's blood that turned her led to forming of the sire bond between Damon and her. As the result, she's more drawn to Damon instead of Stefan as a vampire. She was less tolerant toward Stefan than she was as a human when she realized he was lying and working with Klaus.
How else is different?
As far as I can tell, other than the object of her romantic attention has changed, she's still basically the same person. She feels things she's never felt before, which is common for newly turned vampire because the predatory instincts getting into her mind. But nothing about her has really changed from her human self, or has it? She says she's darker now, darker how?
The only time Elena did act like a complete different person was when she got high on blood and behaved like, as she put it, a crackhead. That was definitely not due to the sire bond, Damon told her NOT to kill, he didn't tell her to get crazy with the blood-feeding. So either that was somehow a temporary loss of control of the predatory/vampiric side, or there's a vampire personality that is different than her human side in there somewhere.