Yes. Because anything you say will sound like you've caved into her "demands"... She needs to realize that you are the prize here, and that you have other options and won't wait around on her. Basically by withdrawing and not replying, you're sort of punishing her.
I can tell by your eagerness to message her that you message her a LOT, don't you? That could be the problem.
It's scary, I know. You think she'll just walk away. Trust me, that won't happen. The more you are willing to "lose" her, the more she will become attracted to you. It's very counterintuitive, but I've made similar mistakes. A while back I met up with a girl on myspace. We hit it off, date couldn't have gone better unless well, you know...

Anyways after I left she sent me a text saying she missed me already, blahblahblah.
I sent her daily texts, things like "smile!", you know, random shit that got her thinking about me. Looking back on it, it was VERY needy and VERY clingy. Then after a few days I start to wonder why I don't hear from her. Then she says she has a BF. Then she deletes me from Myspace. Welp, lesson learned.