Suguha never wanted to bear ill feelings towards people, well, not until now.
The moment Suguha joined Kazuto upon his usual visit of the still-comatose Asuna was also the moment she started harbouring ill feelings to the girl who had stolen her cousin's heart.
The feeling intensified after she saw the famous girlfriend of Kirito. She decided she did not like the girl's porcelain skin – still glowing beautiful despite her long slumber, her long luscious chestnut brown hair, that face that lacked nothing, and the air of elegance oozing out from her presence alone. At that time, extreme dislike gnawed at her heart; she was sure that it had nothing to do with Kazuto giving Asuna the longing look she wished to be aimed at her.
Jealousy grew when Asuna had finally awakened from her slumber. Kazuto was always, always by her side. And if she wasn't there with them, she was all he ever talked about. Though Suguha had accepted long ago that Kazuto, her dearly beloved cousin and adoptive brother, will never love her the same way she does, still, it stung seeing the lovebirds act all lovey-dovey and sweet in front of her. Jealousy was also because of Asuna belonging to an elite family, and the fact that she lives in a completely different world where the Kirigayas could never reach.
Asuna's superb cooking skills, intelligence, kindness, generosity, elegance, beauty and wealth made Suguha wary of even standing next to the girl. The final straw was when they saw her dance. Her movements were executed flawlessly, her body was so flexible and alert and so graceful that it rendered viewers speechless and gaping at her in awe. Kazuto never regained his usual self not until Asuna came and kissed him fully on the mouth in front of everyone out of exhilaration.
Suguha then declared herself insecure.
Insecure of Yuuki Asuna, the daughter of the president of the top electronics company in all of Japan; of her and her intelligence, skills, and simply everything the girl has to offer. Insecure of the girl dubbed by the elites as Japan's Yamato Nadeshiko (Perfect Lady) and the one that holds the heart of Kirigaya Kazuto, Suguha's first love.