Also, how are we feeling now about a possible Stargate to our hell? We have a perfect shaping defense so trying ritual shenanigans in our hell would be pretty pointless, and there are some pretty good precautions we can take-
1. Have the Hellside portal not within the Cities, but within a base in the Frozen Wastes. Maybe the interior Wastes, but either way it would mean that anyone who sneaks through the portal would still have to reach civilization somehow, and any army that manages to make a foothold is dead in the water, especially with Molly having lord of the land.
2. Having checkpoints with required implant interfacing will make it exponentially more difficult for infiltrators to navigate or leave said gate-facility, since no other faction has anywhere near the technomancy skills besides maybe The Wicked City.
3. Self destruct mechanisms are obvious, though it wouldn't kill any invaders in our Hell, just scatter them.
4. Having highly limited designated transports to this facility, full security at both ends of the checkpoints with a whole magitech worlds worth of security precautions.
Now, are there beings that can get past all this? Maybe. On the first, second, or third attempt? Almost certainly not. The Fivefold Courts have a lot of unique properties that would make any attempts to infiltrate require A Lot of time researching countermeasures and trial and error, and that's a timescale in which by the time they DO figure out ways to do so Molly will be far more powerful then she is now.
As for why? Troop transport and trade obviously, the Molly bottleneck is very limiting.