So I have yet to see anyone say this on here, if someone else did then ignore this, but I think I found how to get the ring every time. It's all about what you do during your first visit to Lorelei
It's possible Lorelei matters, but I've found that what you do with Allison in the very beginning is the most important. Often in this game, a single result has a bunch of inputs (and so can be reached in a number of ways).
Secondly, I do not believe it is possible in phase 5 to both turn Lorelei into your love slave with the ring AND turn your coworker into your love slave in the office, I have yet to get the option of visiting the coworker in the office if I pick up the ring.
You can visit Emma if you have the ring, but you can only do so much MC in a single run. So fully MCing Lorelei would probably preclude you from getting Emma in the office, yes (although you never know with this game!).