"Polyandry" sounds like an absolute disaster just waiting to happen.
She's either manipulating the holy Hell out of both of these guys, or, sooner or later, one of them's going to get jealous and want to take the whole shebang for himself.
Either way, I don't see things here ending well for anyone in the long run.
Best case scenario, one of them eventually gets sick of "sloppy seconds" and leaves. Worst case scenario, someone's getting knifed first.