And how will Sauron be able to convince that or somehow "control" her? Sauron had preparation, knowledge, tons of experience and a fair form to deceive others in the past. In this scenario, he has none of that, is facing a fellow immortal that is more powerful than him, incredible patient, self-centered, equally as manipulative, equally as evil, and with 0 interest in ruling the world, more focus on destroying out of spite against the former love of his life (that she know hates with a passion) and the gods. And again, Sauron is an angel, a divine being...Salem doesn't like divine beings.
Sauron also doesn't know about the curse of Salem and even if he somehow figured out and tried to convince her that he can help? She has no reason to accept it, because she already knows a way to stop it that has the bonus of destroying the world, and I feel that she won't take anything that doesn't include that.
Currently Salem has access to a relic that will allow her to ask questions to a nigh-omniscient being(in a hundred years, but she can wait) and another relic that allows her to create basically anything. The magic of Sauron doesn't match that.
Salem may play along because she is pragmatic enough to see a useful ally, but I don't see a scenario where Sauron rules her that way, because for that Salem would have to see him as above her or even equal, which I feel she can no longer see anyone like that. She has becomes too self-centered and selfish to believe in anyone like that