Kim Bo Kyung of SPICA recently revealed on an interview that she was originally set to debut as a 2ne1 member.

She revealed, "I was a trainee in YG entertainment for 2 years. I was set to debut with 2ne1 as the fifth member, however Yang Hyun Seok CEO decided to debut 2ne1 with 4 members and suggested me to a new agency which brought me to become a member of SPICA."

The reason why she only revealed it now is because she was afraid it would bring up misunderstandings and bad rumors and would damage the group's name on their debut. But now that she has officially debuted as a member of SPICA, she has no worries in revealing it.

She also revealed that she learned a lot from being a YG trainee, "They taught me a lot while i was a trainee in YG Entertainment". Meanwhile, SPICA made their debut last January where they released their song "Potently" last 10th of January.

source