Yeah basically what Rhys is worried about is that concerned glances in her direction won't be helpful because of his own expected doubt. He'll admit that he never made it clear to the enemy he's wholly against them, but he'll blame this on being mute. That prevented him from vocalizing an explicit rejection in the dire situations they encountered each other in.

(The reality is that he's flat out told the dragon he wants to save the masked man, but he's not going to bring that up here!)

He'll agree to the plan of them both pretending they might turn, and is also okay with being the only one who fakes it (if that's what you meant by that last part!). However, he'll point out they need to be incredibly careful about Isabella Gonzales either way.