This is all speculation, noone here knows how good/bad her condition is but I think it would be a terrible move if WM decided to push (i say pushed because i don't believe she would leave given the choice) Jine out the group because of her condition, and quite possibly make it worse.
Shes not a kid, and this is her career which shes worked hard to acheive and i believe she enjoys, leaving her without a job to support herself in order to magically cure a condition shes likely to live with for a long time does'nt seem like the answer.
I think she'll be okay, she's a strong cookie & has a lot of support and im sure the fans are more than happy to wait as long as she needs.