The Vampire Diaries -- The Tale Of Two Parties
Did the writers do it on purpose?
One has to think they did, as the similarities and differences between what happened at the party during Homecoming and the ball celebrating the Mikaelson family reunion are rather too stunning to be just coincidence:
1. Elena The Premeditated Murderess:
In 3.09 the minute she came into the room to see Rebekah she was planning to murder her. She brought the sacred white oak ash dagger with her as well as Esther's necklace. She gave Rebekah her mother's necklace and even offered to help her put it on. While Rebekah was touched by the gesture and had her guard down reacting to finally having back her mother's necklace, Elena plunged a knife in her back.
In 3.14, as Damon danced with Elena, he had no clue she was already plotting to have his neck broken by his own brother. As soon as she could switch partners, after throwing herself at Stefan she got him outside and got him to agree to break his brother's neck. Stefan was easy-pickings because he wasn't too happy having the shoe on the other foot for a change and being the brother with his nosed pressed up against the window as Damon got to dance with the girl for once. He was more than happy to put Damon in his place and to rub in Damon's face it was all Little Miss Elena's idea to have his neck broken. Afterwards, Elena lured Damon into a room and Stefan snuck up behind him before he even knew what was happening and killed his brother for her.
In both cases our little premeditated murderess used the justification that Damon and Rebekah were standing in the way of one of her plans.
2, Katherine The Heroine
From the instant Klaus told Katherine in 3.09 that if he died, he'd left orders for Damon to be killed, Katherine's one goal was to save Damon's life. She rushed over to the Salvatore House to revive Stefan and appeal to his love for his brother to put the kibosh on the plan to kill Klaus to save Damon.
While Elena the premeditated murderess got Stefan to kill his brother for her, Katherine got Stefan to save Damon's life. And while Elena put her plan before Damon, Katherine put Damon's life before the plan, even though she'd been wanting to find a way to be free of Klaus for 500 years just to save Damon's life. In short, while Elena was selfish; Katherine was selfless and gave up everything to save Damon.
3. Two Declarations of Love
After Stefan took great pleasure in telling Damon that Elena was the one who put the hit out on him and ridiculing his brother for feeling too much, Damon went to his murderess and told her he loved her. Was she moved? No, she told him that was his problem and basically thought it was no big deal to what she had done to him. And in 3.09 Stefan was just as welcoming to Katherine telling him she loved Damon, after denying she'd ever loved him and convincing Damon he means nothing to her. The fact that she gave up everything she'd been working for five centuries to accomplish, finally being free of Klaus, to save Damon, kind of suggests that love isn't past tense, it's very much present tense. It also seems that Katherine set Stefan up to taking Klaus' coffins to take any target Klaus might have on Damon's back and put it squarely on Stefan's back, instead.
4. Elena Is Not Team Salvatore
In 3.09 Elena tried to get Damon to give up on Stefan and write him off. And in 3.14 you got Stefan to murder Damon for her. In both cases she was trying to sever the brotherly bond between the brothers. The only reason it didn't work is because Damon didn't hold a grudge for what his brother did to him, probably because he's saved his life so many times.
Conversely, Katherine is Team Salvatore as she counted on the brotherly bond to get Stefan to save Damon's life.
I suppose it's understandable Miss Gilbert would like to sever the brotherly bond Damon and Stefan share, as it must be a bitter pill for her to swallow that Stefan loves Damon far more than he will ever love her. He gave her up to save Damon. His love for Damon was so strong it overcame the compulsion spell Klaus cast on him when his feelings for her didn't.
5. Sweet Revenge
While Elena was failing with both Salvatore brothers in getting what she wanted from them: in 3.09 it was getting Damon to give up on Stefan and in 3.14 it was to get her Stefan back; Damon's ex-Katherine was urging Stefan down a path of revenge to make Klaus pay for what he'd done to Stefan in 3.09 and in 3.14 both Damon and Rebekah needed no urging to get revenge on the bitch that killed them by banging each others brains out.
It does seem like the writers purposely used both episodes as a counterpoint for the other; and one thing is crystal clear, the Petrova doppelganger that truly loves Damon and cares about him is Katherine, not Elena.