He thought she was a beautiful woman, more so than Romeo did, even. And when his friend fell for her, it broke his heart, but he dared not protest, because Romeo's friendship was far more important to him than a woman, no matter her beauty, her grace, her kindness…
She was kind, even if it appeared otherwise. He'd spoken to her, become her friend, and then, only then, had he dared to fall in love.
He always retained the secret hope that she loved him back, too, and when she refused Romeo, he knew he should feel guilty, but he just couldn't. Could it be? Could she love him as well, the way he dearly felt for her? Sweet, sweet Rosaline, with her bright, olive green eyes and dark head of hair, her fair complexion and slim figure.
At first, he mocked her. He thought she was stiff, hard, and irritable. And in the beginning, she was—everything about her, said that she was high and above the world around her. He hated that. He was a down-to-earth man, just, though not quite so warm-hearted as Benvolio. He held women in high respect—which was rare enough, amongst men—and haughtiness irked him. So he made fun over her—when she spoke, he twisted her words, in the careful language both of them had grown up with, and shot them right back at her in a humiliating, rather uncalled for way. She, in turn, insulted him back, and on and on they went... She was quite good, actually, but he would never admit anything of the sort to anyone.
He didn't realize how hurtful his words might have been till he overheard her weeping, confiding in a friend that she was tired of the constant debate, that she was a human being—
He walked away from the door about then, because he did not want to hear any more.
Romeo caught up with him, asked him what was wrong. He could not answer.
After that, he was a little kinder. He spoke courteously, and she answered in the same manner, and, just like that, they were taking walks and talking, and laughing. It was quite odd, he knew, because they weren't betrothed, but they were related very distantly, so he could act as her brother, as Tybalt was to Juliet. He began to call her Rosa.
And then Romeo, that fool, went and exchanged a few crude lines with her. The boy had no idea what he was doing wrong, no idea that this woman, this fair, sweet woman, was a human being, not some toy to be delt with whenever he thought pleasurable.
It was with his friend's declaration of love that his own affections began to form. She was his friend too, was she not? It wasn't an unreasonable match. He was not a Montague after all… And she'd refused Romeo.
When he asked her for her hand, she gave him a long look and asked him why he would do such a thing to the both of them.
Because he loved her, he answered softly, unwillingly.
She kissed him first. She was that kind of woman, not exactly bold, but not submissive, either, and soon enough she was pressed against the wall, and he was kissing her red, red lips…
She shoved him away and told him she would marry him.
He was easily excited. Mercutio, up and down, moody and wise. That was the day he fought Tybalt, that was the day he was killed—when the last thing he saw was her smiling face.