Am I right?

I don't get it :(

Between three people, male and female, straight or not, there will always be one relationship. Try the combinations. Let’s say there was one straight man and two gay women. The relationship would be between the women. If you can think of a combination that doesn’t work I’ll be shocked.

three gay women who are all single

That works

no it doesn't

Ok then, explain how it doesn’t work. Two of the three could be together.

but they aren't together

But they could be. That’s the joke.