You might need to be a higher level. I'm sure she'll call you eventually, have you done the quest for Elysana?
rrr... I'm level 18
No I did not do that Robe's quest. I did not do the Robe quest... Thought it would prevent me from doing Barenziah's, but I may have got it wrong?
Btw although I did finish Helseth blackmail (and gave him the letter) the topic Castellian still shows up in my dialog options (the quest should be over, as says on the wiki.
EDIT: OK - I had misread about the Robe quest, doing it was necessary for the Barenziah Book. Sometimes that ques-gramm is not so clear.