The Shall'ille Disciple Quest is not bugged. It is a little confusing however, so here are a few guidelines to help you finish it.

First, the target of your quest will not respond to your message. If you get a response, then the message is not considered received. Properly, they should be shamed to speechlessness by your words. (also, note the distance at which you can get the priestesses to respond to your requests for spells and the like. IF you aren't at least that close, your message will not be delivered)

Second, you cannot be a disciple without the acknowledgement of the priestess, so return to the Shal'ille temple and let her know you have delivered her message. She will acknowledge your success and welcome you into the faith.

Source: GuardianCorliss