Why did she say yes?

Detention

Elena said goodbye to Caroline and told her that she would call her later.

It was time for detention...

Elena was happy to be in detention because she needed some time to think. She was alson curious of who's going to be there. She was hoping for a certain blue eyed Salvatore to be there.
Elena opened the door to see her teacher next to a pile of work sheets that she assumed were for her.
She sat at the back of the class only with three or four students in front of her. They were all with their workbooks open with their cellphone hidden.
It had past like an half an hour, and she was really tired of doing all that work, when she heard a knock on the door. He tried to see who it was but she couldn't, all she heard, "Elena Gilbert is needed at the principal' office, Principal Jones sent me to get her. Can she be excused of detention?"
"Of course."
Elena was really confused, why had the principal called her? She did nothing wrong.
"Elena Gilbert you could be excuse of detention!" Her teacher called her.
She packed her things and opened the class door to see the one and only, Damon Salvatore.
She was really surprised and had a lot of questions.
"Damon what are you doing here?"
"I come here to save you from dying of boredom!"
"That's really sweet Damon, but does that mean the principal doesn't want to see me?"
"Of course not Elena, it was just to get you out of detention"
"So where should we go? We can't stay here, next to detention?!"
"Leave that with me..."
And she did. Elena was really happy that Damon was the one who saved her from detention, she was really surprised with herself, she wasn't that kinda of rebellious girl, that skipped detention to go be with a boy. She couldn't wait to tell Car everything.

Damon stopped. Elena could see this was a really beautiful place she never been before, she could see a bench and a beautiful landscape with a lake and really cute ducks.
"What is this place?"
"I found it when one day I skipped detention and decided to explore the school property. I come here a lot, to think and sometimes just be alone from all the drama. I always wanted to show you this place, but I was afraid Stefan would be hurt or something."
She'd never seen this side of Damon, the cool kid. Her feelings for him were becoming more and more intense by the minute.
"It's really beautiful Damon and peaceful."
"I know, I always thought of you when I came here "
Elena started to blush
"Damon I never thought you were this sensitive!" She teased.
"Oh!Shut up!" He looked into her beautiful brown eyes.
And she blushed even more.
He noticed the effect he had on her and to calm her down he held her hand.
She started to giggle because that's what she did when she was nervous.
"Why are you laughing Elena?"
"I'm sorry, it's not you, it's just when I'm nervous I start to laugh!"
"Oh... Why are you nervous?" He already knew the answer.
"Don't laugh okay? Promise?"
"Promise."
"I always wanted to tell you something but I never did. I have feelings for you Damon Salvatore and kept them bottled up for too long! Stefan and I started hanging out last summer and he tried to kiss me several times, but I never let him because of the way feel about YOU. When he finally asked me to be his girlfriend, I gave up. I realized that you would never feel the same way I do so I said yes to Stefan knowing in my heart it wasn't the right decision. I don't see Stefan in that way, he was my best friend so what better way to get over you than to be in a relationship with a guy who knows me better than most people?"
I saw Damon's face and he didn't look surprised at all, like he already knew everything I just told him. I really wanted him to say something.