There's no rhyme or reason to the yo-yo effect. What's pulling her back to the other universe other than the script? It's this kind of arbitrariness that has made Olivia Dunham's superpowers a dramatic stillbirth. The show has never established Peter as mentally competent (indeed, it generally shows him as incompetent,) so him finding out about the fake raises no expectations he'll save Olivia. Walter the lunatic will be replaced by Walter the supremely able mad scientist who grabs solutions from his ass.
The only reason to hide the parts of the Vacuum (that name's as inept as "Massive Dynamic!) in two different universes is to keep them from being found by anyone else. Therefore broadcasting the coordinates is insane. Further, the First People have to still be around in some form, either personally or by AI, to update the coordinate system in the broadcasts. But if they're still around in some fashion, there's no need to broadcast the coordinates at all! The whole thing is doubly insane. But, killing people deciphering the numbers so that the Fringe Division deciphers the numbers is manifestly an insane plan, so at least the show is consistent.
Mythology is not the show's strong suit. Come to think of it, it doesn't even have a strong suit, it's got one high card, Walter. There hasn't been enough Walter this season, and they keep reducing Peter to cardboard, and they ignore Astrid. This season has been awful so far. I keep hoping they'll get back to Walter (and Peter and Astrid,) and it's just more Olivia. Double doses of that aren't working. I'm not sure I can take much more of this. I keep thinking of Newton telling the other Olivia she isn't hard enough, then she lies back and thinks of her universe while Peter does his thing. The notion that the other Olivia cheating on her boyfriend is a bigger sacrifice than all the killing she's done is rather an unpleasant way of thinking.