"Many can manage two octaves in their lower register"???!!! Who are these paragons? Streisand probably could, and there are others but it's not common and it's not the same situation as with the male voice.

Chest voice is just another name for lower register, but in many/most women its range is pretty limited. Remember, "two octaves" means that you can sing the note in 3 different frequencies (for example, G below middle C, G above middle C, and then G the octave above that). It's a mighty woman who could manage this using only chest voice, though some can. In most cases however, I wouldn't give you a plugged nickel for what they are going to sound like in a few years' time.

Breathy-baby-voice does not have to be synonymous with "head voice" though it often turns out that way in practice because it's not our natural speaking voice (think of kids in the schoolyard mocking something in a high falsetto) which tends to be stronger. But, as you say, it's how that voice is used that makes the difference.