I'm definitely waiting for her to bring it up.

I'm imagining something like this:
You've brought this up before and I've had some time to think about it and look into it.

My first reaction is that if some of the money that I bill goes to you, then you need to write me an invoice for it so my tax paperwork can show I don't need to pay taxes on those amounts. Otherwise I'll be paying income tax on money that's going to you. And you'll be getting a 1099 from me.

Next, you don't want me to change my rates. That means that I'll have one client from whom I earn less money than all my other clients. The actual result of that is that ALL other clients are at the top of my list except for this one. If it were you, would you respond equally to all clients?

The law is pretty hard to interpret on this, but it might be illegal. If you have a contract with the client that says you hire me and you tell me what to do and you charge the client an amount that's a fixed percentage of my billing, then that's okay. And that might no be okay since you don't have a contractor's license.

A major part of that last bit is that the client needs to know an authorize that you are getting payment as a part of what is paid to me.

End of statement. That's how I'm rehearsing it, but it would probably come out a bit more friendly than that seems.

In the commercial work I do, everyone recognizes that the GC has no idea what I'm doing. There's no way he knows enough about it to tell me when to do different things, and he doesn't know what needs to be done. So I'm hired by the client separately from all the other trades. My interaction with the GC is to work with his schedule and do things in a way that doesn't delay the project. The GC does not earn any money in this situation because he's not doing anything except be open about his schedule... which he has to do anyway.