Well it's really hard to tell without knowing the rest of the chapter because I suspect this is a structural problem.

The core of this scene is supposed to be Dee crying. Though structurally, the moment that's supposed to be the climax of the scene instead is when Robert und Cottle come in, and when Hoshi talks about Robert. But that's not important for the story you're telling right now; it's just plotty set up for something that you'll do later. So you're marginalizing Dee's reaction. But you're saying that you wrote it before without that interruption, and it didn't work. So I'm not sure. It's hard to navigate blindly.

I bet the actual problem is somewhere else. If the exposition is broken, the climax can't work. :) It looks to me that if you've sufficiently set up Dee's emotional developement, you should just be able to have her start crying without any explanation or trigger whatsoever. It should work. If it doesn't, then that's because you didn't set it up. I've seen this before. Hell, I've DONE this before. :D

Feel free to send over the chapter if you want me to have a look at that.