I couldn't begin to rap my head around this game, it was as if Ao Usagi himself made it; though I think the real ending is more positive than this. When she jumps off at the end several dream creatures show up leading me to believe when she "died" she left the dream realm behind permanently and returned to reality.
It depends on your views of death and the afterlife. A common interpretation, and one that this comic tends towards, really is a happy ending. When you consider that her life consisted of a tiny room she couldn't leave, a TV that didn't work except for the depressingly futile NASU, a balcony that allowed her to look at but not interact with the world and no family to speak of, she didn't have many things tying her to the land of the living.
On the other hand, once she fell asleep and entered her dreamworld, she met fantastic characters like Kyukkyu, Tokuto, Poniko and Uboa, the monochrome sisters, Seccom Masada, Kasei-san, Kamakurako, the toriningen, and so on. Sometimes it was scary, but it was a lot more interesting than her real life. She killed herself to "live" forever with her new, and only, friends. The afterlife as your dreamworld isn't a bad way of looking at it.