At the very least, Sam is being disingenuous. At worst, she is full on shit stirring, enjoying getting you to doubt your own mind, and trying to cash in on your H's blatant attraction to her. All the while claiming to be an innocent victim who hasn't been stirring up trouble at all...
Perhaps she has a need to establish herself as top woman, the one everyone's husbands wish they could have...
She seems to like playing games, toying with people's feelings.
She tells you about Pamela's dream that she, Sam, was up to no good with your husband.
She also tells you that Pamela thinks that she, Sam, is inappropriate with her, Pamela's, husband.
She tells you Pamela is insecure for thinking this. So if you, like Pamela, also think there's inappropriate behaviour going on, then that must be because you are insecure. So she is setting you up to doubt your own thoughts and feelings, because otherwise you'd be as bad insecure as Pamela.
And that has worked nicely, because you are now doubting yourself, blaming yourself, feeling insecure, feeling ashamed of feeling insecure...
Why do you think she told you about Pamela's dream?
Did she tell your H about it? Or do you think she wanted you to tell your H? Then he'd have an image in his head...
Does he actually know about Pamela's dream? Did you tell him? Did she?
Have you actually asked Pamela about this dream, if it's actually true that she had it?
Why would a genuine good friend tell you about that dream? What possible decent reason could there be?