Isolde's expectations may differ due to how things are handled in Orlais, rather than how things operate in Ferelden under Greagoir's watch.
Rhys and Adrian talk of being allowed to visit Val-Royeaux in "Asunder".
while a child like Ella tried to leave the Circle in order to let her mother know what happened to her.
Unless Ella is not from Kirkwall, there's no way her mother wouldn't have know where she was taken.
Ah, my mistake, I thought you were referring to something else. Anyway, Kirkwall is different in that mages are highly accessible. You see them walking around all the time in the Gallows. You can even chat with them (though apparently they're punished for it at times).
Obviously, if the Circle is built in the middle of the city, it's easier for people to visit their mage relatives.
However, Isolde is still the arlessa. She can afford to travel to Lake Calenhad and visit Connor.