It is unclear if the “God” Kaneki mentions is in fact Eto or rather an allegory, but she fits the context. If any of this is true, it may give credence to the idea that she wants to completely subjugate him by severing his connections with those he cares for. As I said, Eto projects herself on others a lot. So when she was telling Kanae in order to become a person's "most important thing" that he must first take away that person's "most important thing" - I got the impression she was projecting her own desires to draw Kaneki towards her. Granted, this is only a theory but it coincides with Eto's warped and demented thought process. Destroy his relationships until he falls into abject despair and has no one else to rely on.