I still want to know, if she has a terminal illness. His resolve seems to be faltering, but she definitely steeled herself to go through with her decision. The candle who burns the brightest, burns the fastest, so I guess she wants to enjoy life before her suicide.
Still hoping for a happy ending with both of these alive, but I don't see it at the moment. Especially not for her. Maybe we will see him getting his life together after him crying at her grave and thanking her for all the times they shared and a short flashback over the whole manga as the last few pages of the last chapter. Manga authors tend do these kind of things. Still not fond of the whole "thank you for teaching me a lesson to make me a better person-tragedy end, though.