I have been courted for months by the girlfriend of a major producer/director in order to get me to take my film to him

That's a great opportunity. You should consult with a business/entertainment attorney who can help you with protecting your interests in your idea and the amount of money that will go to either or both of them. Good luck

Her rights to an agents fee comes from her client (boyfriend/producer) and not from you.

Hire an attorney, You are swimming with the sharks.

The agency fee due her, if any, will be paid by someone other than you. That said, why are you co corned with protecting her position rather than your own? Your question seems confusing in that regard.
It seems you should be Tali and care to assure that your project is properly protected before being disclosed, and that your interests are accounted for moving forward, respecting registration of your work, and contractual protection of your ownership in the project.
Perhaps I'm missing something here, but again I'm lost as to why you're seeking to protect someone else's girlfriend, perhaps at the expense of yourself.

Get an attorney to embody the terms of your agreement. This would be addressed there if at all.

Please make sure your film is copyrighted. You can find a link to the copyright form on my website http://colleenkerwick.info. It is the Producer/Directors responsibility to pay his girlfriend, not yours. Sounds like you are losing your objectivity and need an attorney. Don't be played.