Marius was not Eponine's first love among the Children of the Barricades.
Before him, she had been greatly drawn to their leader, handsome Enjolras. He had such dignity in his bearing, such passion in his speeches to his comrades about the revolution.
Most of all, however, he was untouchable. Aloof from the others, even from his closest friends, as though his nobility put him on a higher plane than the rest of the world. It was this that eventually led Eponine to transfer her affections to Marius.
But when she saw Enjolras fall, a piece of her died with him.