its called co consciousness. co consciousness is how much awareness there is between the host(core) and the alters.

each persons system is set up how ever they need it to be, your therapist saying this means your internal system is set up so that some alters are co conscious (aware) at all times of what is going on, being said or done with you.

alters share the host(core) 's body. that means they hear just like you do, through the ears. they eat the same way you do through placing food in to the mouth,....they talk to your therapist by speaking with the mouth..

you dont know what your therapist and the alters are talking about because you dont have that level of co consciousness yet.

keep working with your therapist and maybe you will be able to develop more co consciousness (awareness) between you and your alters.