So... I need help with this. Any and all ideas would be appreciated.

I had a needy sixteen-year-old student this past school year who could not seem to do any combination I gave the class without first asking me at least one question about it. Time and again, I saw her actively "shut down" and stop watching me demonstrate, and instead focused all her energy on trying to get my attention to ask her question. I tried saying things like, "I'm still teaching this, so keep watching me," and, "Hold your questions until after you've tried to do it once." Still, she seemed to need my one-on-one attention or she couldn't/wouldn't do the combination. Her constant questions took up a tremendous amount of everyone's class time.

When she returns in the fall, I'm considering creating some kind of policy for her class like, "no questions until the end of class."

What do you think?

I would try to talk with educational teachers who have been taught about different styles of learning. It sounds like she is processing the combination you are demonstrating, but, as soon as she has a question in her mind, she needs it clarified NOW, before she can listen and watch the rest of the combination.
I would try this: give her a piece of paper and pencil and have her watch the combination and when she comes to a big question just make a slash on the paper, and not think about it anymore. Then her mind knows it is noted and her mind will let her concentrate on the rest of the combination. At the end of the whole combination ask her what the question was.

good luck

My experience is that such girls are very insecure (but usually they wait untill the end of my explaination), or have huge concentration problems (they don't see the organisation of the instruction at all, because they don't have such organisation in their heads). It seems to me the latter is the case here.

Explaining THAT to them often helps them to see why all their questions aren't working: "Dear, your brains seem to work differently than mine. Since you are younger/ I'm older I ask you to make your brains work my way. (I'm too old for changes.) First I explain the complete exercise. And when I'm finished I will ask you all if you have questions about the exercise. That's the moment for you to ask."

Do it exactly like that for a while. Keep asking for 'question?' untill she gets the routine of that. Could take months.....

If she is insecure, talk about that with her in privat. A 5 minutes talk one on one can make miracles happen.

I have TWO of these cases who dance with me year-round. One needs a clarification of EXACTLY what I just said EVERY time (UGH!) and the other does the "hand in the air" the second she has an idea for a question. SOMETIMES, its just a little personal attention they are seeking. I nipped the first case in the bud by pulling her aside and discussing the matter with her. The other girl really just wants the attention. I like the idea of reminding her she HAS to try the combination first before asking a question. It may solve your problems.

I don't limit the number of questions that my students have, but sometimes I will ask them to see me after class for clarity or something along those lines because I cannot take up any more time going over things. I've always been a dancer that asked a lot of questions, because I almost feel like I have the need to make sure that I'm doing it correctly, so I remember that when I'm teaching. I have found though that the best way for me to teach combinations or new steps is to demonstrate it once or twice by myself, and then take it one count at a time with the entire class following along. I don't answer questions until after the entire class has done the combination at least two or three times. It might seem like I'm taking up class time with the way I teach it, but I have found that it cuts down on a lot of questions. Do it myself, and then they do it with me a few times. This way they are kind of processing the step while following along so that they can see whether they are doing it correctly or not.