I dunno but . . .

. . . just because she may have rejected one agency -- or more than one -- tells me nothing.  After all, her career is fucking for a buck.  

Approach her.  Be nice.  Tell her you are a big fan.  Give her your business card with your references and hobby cell written on it, maybe even the names of some girls she would know, all wrapped in a hundred dollar bill.  Tell her you are a HUGE fan.  Fan an appropriately sized display of Ben Franklin portraits.  Let her know if you are AIM tested.  Maybe you are a gonzo film producer, I dunno.

Just because she may not be willing to sign up to fuck anyone an agency puts her with doesn't mean she may not be willing to discuss the situation with you.  You may strike her as her flavor of safe and nice.

Even if she flat out says no, tell her what an honor it was just to get to ask.  She may still mull on it and dial your digits.  

There is one sure way the answer is no:  If you never ask.