Sakura could never explain it. She loved Sasuke just because. Not because it was written in the stars, not because she had to, but because she couldn't see herself with anyone else.
No one had forced her. In fact, everyone discouraged it. Ino called her an idiot and Kakashi-sensei had only been kinder by a few degrees. Even Tsunade-sama had advised her to "get over Uchiha. He's no good for you."
Sakura is too smart not to realize this. Sasuke consumes her, drives her, eats away at the little pieces of her spine; he is the stain on her soul that she cannot wipe away.
She could easily have dated other boys, other men, like Lee and Naruto. Naruto would have saved the world for her and Lee would have given it to her on a silver platter. But Sakura doesn't want Lee to give her the world on a silver platter, and she most definitely doesn't want Naruto to save the world for her. She wants Sasuke to be the one to save her, to give her the world and himself. And it hurts her to know that, no matter what, Sasuke won't do those things for her. But still, she loves him because she can't do anything else.
And she knows: it's not fate. That would have been the easy way out. She made her choice when she was twelve and at sixteen, she has not changed her mind because she can't change her mind. It does not matter that Sasuke had no eyes for her (he probably can't even remember her name). It does not matter that Sasuke chose to seek revenge and Itachi over her (he left her crying). She can ignore her regret and she's learned to shut off the part of her mind that calls her a fool. Because at twelve, she had fallen madly in love, and at sixteen, she has rooted herself in it so deeply that she knows she will never be able to dig herself out.