basically she wanted to start her own company selling clothes. she also started seeing this hong kong business man CEO dude. SM (her company) didn't like any of that.
they were like you can't balance SNSD life and business life but she said she could. so they threaten to kick her out. also SM supposedly told the other girls to push her out of the group. jessica then basically said good bye to everyone on social media and then SM just went up and kicked her out of the group.