Read Maty Ezraty's repsonse:
Teaching yoga is very much like parenting. Parents must discipline their children, because a misbehaved child who is encouraged will become a very problematic child. The sooner you address this issue, the better. Therefore, if you are answering all this student's questions in class and letting the other students suffer, you are helping her to be more problematic.
This student sounds difficult, and I recommend that you speak with her privately after class. Start by letting her know that you enjoy her as a student and that she has many valuable questions. Then proceed to explain that it is very difficult for you to answer all her questions in class, because it takes all your time away from the other students. You could also suggest that she take a private lesson with you so that you can answer her questions. Or, if you have time and are willing, ask her to save her questions until after the class is over.
If the talk goes well and she returns to your class, be prepared to remind her of your talk and to help her stay with the group. If, on the other hand, you lose her as a student, this might prove beneficial to the rest of the class.
Maty Ezraty is co-creator of the first two Yoga Works yoga studios in Santa Monica, California. A former YJ asana columnist, she travels around the world leading teacher trainings, workshops, and yoga retreats.