Proxy Play versus Cuckolding?

[Deadman]

I’m curious what the difference is between the two. I’ve been playing with a story idea and the idea of proxy play has come up.

However, I wonder at one point does it end up becoming cuckolding?

Here’s the general idea, Mary and Sarah have unresolved sexual tension between each other and while not being willing to talk about it or get it on with each other, they will sometimes sleep with each other’s male exes. Sometimes Mary is there when Sarah is getting it on with a guy and other times Sarah is there when Mary is getting it on with a guy. Or one of them mentions it to the other later.

As the subtext between Mary and Sarah becomes text, is there a point at which it becomes cuckolding? Do Mary and Sarah have to have actually slept together before the proxy play becomes cuckolding?