Funny about this scene...
I do kind of view it as being along the same lines as Wes Parmalee --- is she or isn't he/she Jock/Pam? The question is as intriguing as all the possible answers.
But then, almost everything after Pam's Dream is negotiable (or shortly before, for that matter, given Donna Reed's brief casting).
It's like visiting Southfork today: something's missing, but the ghosts hang large.
I thought the scene with Margaret Michaels was well-done, hauntingly scored, and, yes, surprisingly effective... But was it really Pam? I could even devise a rationale for it being an early and elaborate attempt to rein in Bobby, going through Cliff, of Jeanne O'Brien. But when Bobby said, "Goodbye Pam" after his final scene with Jeanne, I had the feeling that the writers were also saying goodbye to Pam, and that's pretty much what they did.
We need some wrap-up for Pam before 2013. I vote for their finding out Pam might be dead before 1991, with neurofibromatosis being the culprit -- she was Digger's daughter after all!
Likewise, JfL had a good plot idea with Miss Ellie confessing on her death bed that JR was Digger's son, leaving JR meaner than a hornet at being Pam's and Cliff's half- brother! (Don't worry -- we can have DNA tests undo it by series' end).