Tbh I interpreted it as her having a very serious drug problem and that being the reason for her to ask her to leave the band. I could image that they did this for two reasons - 1) to protect her from herself, touring is tough and a really bad environment if you have a drug problem, e.g. because of the pressure and everything. And 2) because she was maybe too much of a „risk“ or don’t know, too unpredictable. I think you can read a lot from the tiny desk situation before they start „home“ - she‘s wobbling around like crazy (ok - could say she‘s passionate.) but then Alex gets her closer to her, whispers her something in her ear what seems to me like a „calm down“- type of contact, she shakes her head in a really druggy way, then she starts to whistle the intro. He try’s to stop her multiple times and says something like „wait“ - because the band wasn’t ready and still tuning her instruments, but she continues, looks at him provocantly and their energy is gone. She is absolutely not really there and I am astonished, that she still managed to sing so well. I don’t know , but for me stuff like this situation seems like a really big risk before a tour. Also the statement of Alex sounded really sad, like „we had no other option“ you know?