I feel like Taeyeon and Jessica might have been close at first when they debuted, but somewhere around 2012 something happened where Taeyeon and Jessica had an arument, or Tae got sick of Jessica and started acting cold towards her, I remember reading in 2013 that Sones were worried because it looked as if Taeyeon stopped speaking to Jessica completely. Even in this video you can see that in all the videos from IGAB on Jessica is the one always hugging and smiling and playing with Taeyeon while Taeyeon either smiles indefferently or remains unresponsive. I think that Jessica wanted to fix their relationship but Taeyeon wouldn't budge.I think that Jessica and Fany were cool with eachother, I think Tiffany did sincerely care for Jessica. They were good friends got along well but were not BEST friends. I think Jessica got along so-so with Sooyoung and Hyoyeon. They could talk once in a while and joke around but it was all mainly professional. But I bet there were times where they both couldn't stand Sica. I think Seohyun saw Jessica as an unnie that she loved and respected and looked up to, but not like a best friend that she would hang out with on her free time, they have different personalities and a different sense of humor. I think Yuri & Sica were cool in the beginning. They could talk and joke, but they were never truly close.Idk what the deal was but I think that at some point towards the end, Sica and Yuri were not on great terms. I think the only members that Sica was truly truly close with like sisters were Yoona and Sunny. Although Sica sincerely did love, care, and respect all of her members. So I think that if for whatever reason Taeyeon might have brought up the idea to expel Jessica from the group because she felt like Jessica didn't treat SNSD as her priority. Yuri, Sooyoung, Hyoyeon, and Seohyun might have agreed to it for the group's sake. Tiffany would have been sad with the decision, but might have agreed in order to support Taeyeon because Taeyeon is her bestest friend. I think Sunny might have rejected the decision at first, but then for some reason ended up agreeing to it with pain in her heart. I think Yoona might have been the only one that ultimately said no.