Hope that the next few chapters have the crew visiting senpai. I don't know exactly what's up mentally, apparently extreme introversion that causes complete burnout or something, but I do know that being alone in your room does not help any sort of depression.
That's not to say she's gonna be cured (don't think this, like a lot of mental stuff, has cure) by everyone running into her room, yanking her out of bed, and yelling "GET BETTER, BE HAPPY" is gonna work (it definitely would just piss me off if someone did that to me during one of my depressive periods), but just coming over and chilling, not even talking about why she's out or anything serious, just making sure she stays connected to everyone and that she knows people who give enough of a shit about her to physically come over and hang out would definitely help. That last panel was haunting, to say the least.