Disclaimer: I do not own Vampire diaries and any of its characters
Sorry if this is really bad, it's my first story and I just wrote it because I had the idea that in every fanfiction i've read so far, Elena always cries when she finds out Stephan is cheating on her. This is my view on what she would (should) do in this situation.

She just stared in horror as the image of Stephan and Katherine unrolled right in front of her. Rage began to flood her soul, her brain; God she thought, I'm becoming more like Damon everyday!
What made this event even worse was that they were going at it like rabbits at the tomb entrance and Elena could see everything; of course if she focussed enough she would be able to picture herself as Katherine; Stephan's arms protectively trailing down her body, causing her to moan as he stroked her sensitive spots; but she knew that was not the case, she was the mirror image, nothing more; she couldn't feel the pleasure from his touch, but Katherine could and that made her feel mad and deprived.
What seemed like hours later, Katherine turned her head to face Elena (obviously catching the scent of her blood). She stared for a few seconds; no emotion evident from her stern face. It didn't stay like that for long... a malevolent smirk slowly replacing it, it was like a nightmare. In just the same motion as Katherine Stephan turned his head noticing Elena, and reacted by immediately doing up his fly, obviously feeling it indecent of him letting Elena see him making love to her doppelganger. The rage Elena was beginning to surface yet wasn't evident for long as after touching the cold air, it evaporated into tears; all she could think of was running from the world, from the tomb and from life. The moment she reached the top of the stairs of the tomb she hit into a firm body, a masculine body... it was Damon.
"Come on, let's get you home" And as if by magic, Elena was lying in her bed with a rather sexy looking Damon hovering above her. She gasped at how irresistible he looked and knew the rather intimate thoughts entering her head were invented due to her neediness; she contemplated taking him right there and then. Anything couldn't be as bad as what Stephan did to her... could it?
"Are you sure you'll be okay?" He stated; his voice sounding cold without emotion.
"Mmmm", her words had become incoherent and were replaced with moans from the predator inside her. She just wanted to leap onto Damon and watch the evening develop into a night filled with pleasure, excitement and above all, she wanted it to become a night of forgetting about the world and more specifically, a night where she would melt into Damon's strong masculine arms.
"Ermmm, I better get going" Damon was practically screaming at himself, she was showing all the signs of a needy woman; her legs were spread wide, her heart racing (occasionally skipping a beat) and her hot core was wet; he could smell it.
No Damon, she's just seen Stephan cheating on her, all she wants is me to be her rebound, nothing more. But as she wriggled on the bed, he re-thought his intentions, after all he wasn't Saint Stephan, he was Damon, the hottest bachelor in Mystic Falls and he was not going to miss out on a free shag.
Elena let of a girlish yelp as he jumped her; this was not what she was expecting at all, she thought that he would've been a gentleman and left her to be alone in her thoughts and fantasies. This was obviously not the case.
"Damon..." she panted between their kisses; she had to admit that every time his lips touched hers, a jolt of electricity went up her body, he was perfect but it still didn't seem right.
"Damon!" She yelled, pushing him off her with full force. She immediately regretted her actions; the moment his body was off hers, she felt incomplete, she needed him but at the same time needed to be the better person.
"I thought that was what you wanted?" He looked adorable confused. Maybe he read the signs wrong; maybe he jumped to a conclusion without thinking about all of the possibilities.
"It was... It still is. I just want to be the better person, in theory I'm still dating your brother whether I want to or not! I need to officially break up with him before I let you take advantage of my body... the body of a single woman"
His eyebrows wiggled with enthusiasm. He had gotten what he wanted and he didn't even have to move a finger to get it, Stephan had screwed this up all on his own... well with the help of Katherine of course.
"I'll do it tomorrow... I just want to be left alone tonight, if that is okay with you?"
Damon nodded in agreement and began to walk to the open window, but something in his brain forced him to turn around and look back at Elena.
"Just Remember, you owe me" He smirked suggestively and vanished into darkness. Elena let out a brief smile, she knew that he would one day be her prince of darkness, and she would be his princess... but right now, she had business to take care of."