Is there a way to make a lesser PU partner revoke their protectorate?

I'm playing as England, going for the Master of India Achievement. The year is 1730 and I've got the lower 50 percent of India. Now I contested a Spanish succession of the Portuguese throne, so now Portugal is in a PU under me. This gives me an unforseen problem, because Sind (which holds provinces I need) is a protectorate of Portugal, so I cannot attack them. Is there a way to get around this? Can i maybe let Portugal give Sind up in a peace deal with another nation?