Is Nicole dead or is she just a necromorph?

New Arrivals N
Intensive Care I
Course Correction C
Obliteration Imminent O
Lethal Devotion L
Environmental Hazard E

Into the Void I
Search and Rescue S

Dead on Arrival D
End of Days E
Alternate Solutions A
Dead Space D

Thats a funny little thing from looking at the chapter names. Also answers the question.

As far as the marker goes, from the audio clues "make us whole again" it makes it seem that the marker and the Hive mind are more linked than just a suppression tool. With that said, the hive mind would work to get the marker returned to the surface of the planet and back to itself. As well as once taken away from it would pursue its thief to try and resecure it. However if that is what it truly wants then why are the Necromorphs attacking you throughout level 12. That is where this hypothesis fails. If the hive mind wanted the marker back then it would not have impeded the work of Isaac for the last 2 levels, however it is probable that the distortion the necromorphs cause on the human corpse makes it little more than an attack animal, without the ability to be really controlled once created. Speculation is little more than such however as there is not enough information to go off of to make anything more concrete than speculation.