She released her solo album entitled Elly Is So Hot (the name "Elly" is a nickname that Seo created for herself) on February 26, 2007. Known as the sexy dancer in the group,she has stated that she wanted to move away from her strong dance image and become a softer, elegant, more sensual entertainer.
The first single from the album was "Neoreul Wonhae" ("너를 원해", "I Want You"), which was written, composed, and produced by Jung Yeon-joon, from Uptown. Originally a mix of Latin and R&B styles, the song was promoted with a dance remix near the end of her promotional tour.
It was announced that In Young would be releasing her second solo album titled Elly Is Cinderella on July 23, 2008, with the lead single "Cinderella" composed by PSY. Her album was released on July 23, 2008.
On February 2008, Seo In Young participated in the MBC variety show We Got Married. She was paired with K-Urban artist Crown J. The duo later released the digital single "Too Much", on May 19, 2008. The song was used as their theme song for the variety show. A club remix version was also released on her new album. She also sang "Can't I Love" for the OST for the Korean drama IRIS.
It was announced in December 2009 that Seo In Young as well as fellow Jewelry member Park Jung Ah would be leaving Jewelry after completing promotional activities for Sophisticated and fully commit to their solo careers.
Seo In Young released her third album called "Lov-Elly," her first album without the label of "Jewelry's Seo In Young," on June 6, 2010. The album consists of ballads, showing a very soft but powerful side of Seo In Young. Her album-jacket and first single "Goodbye Romance", were released May 12, 2010.. She also joined the new SBS Reality Show "Heroes" in July 2010, receiving a lot of press and controversy for her feisty and headstrong persona.