Your best chance to see a woman play in the NHL may be a goaltender, and even that may never happen or at least be a really long ways off. Your best players in the world currently maybe could hang a bit in the ECHL, and I'm not even sure that's a guarantee. Szabados was considered the best women's goaltender in the world and during that time she was in the SPHL.
As far as skaters go, there just isn't the same power to compete at that level. The best of the best in the world are supremely skilled, but they're still well behind what even the replacement player NHL player does simply from a physical standpoint. If you watch actual game action (not skills competitions) the shots come off less quickly, don't have as much velocity....every minute aspect of the game happens a full step (or more) slower. The US women played exhibition games against Tier III Junior A teams in Florida...Tier III Junior A is a fancy way of saying Junior B, and the level of teams they played there were quite low. Those games were like 8-3 wins, against supremely subpar competition compared to what even a press box NHL'er.
Women's hockey is better than it's ever been and will continue to get better. The best of the best in that world are amazing hockey players and could skate circles around probably 90% of this board, but people really, really need to back off this "so and so should be in the NHL". Doing this would set women's hockey back God knows how far, because they would be utterly out of place at that level and look terrible and it would just smear women's hockey to have the best of the best in your sport fail so miserably. It would be a terrible look and I'd hate to see it.
I'd love to see one of the ladies get a shot in the SPHL or even the Coast. I think that would be much more viable and if they do that well there, then you evaluate moving up the chain. But there is not a woman in the world today that could hang in the NHL, not even close. And that is not remotely a dig at women's hockey, it's an acknowledgement of science and physical capability.