The Secret Lovers

Seo Young Ji was from a poor upbringing and worked as hard as she could to better herself. She went to see a plastic surgeon, hoping that by changing her appearance she would have a better future. The surgeon, a beautfiul young woman called Jeong Ah Mi, asked Seo Young Ji for a favor. Jeong Ah Mi had been set up on a blind date with Kim Jun Woo, but she really had no interest in going. So she asked Seo Young Ji to go under false pretense. Seo Young Ji agreed to help out with the intention to turn the guy off but the blind date was a hit and the two started dating.
Add to the equation Choi Do Kyeong, a poor but ambitious social climber, who would do anything to marry rich. He rejected Seo Young Ji as she was poor and did his best to go after Jeong Ah Mi.
(Source: DramaWiki)