It definitely was that. Being able to keep the anger down and act in a measured fashion is the mark of a strong individual, respect for that.
There's a quote that comes to mind when it comes to matters of family:
It's a tad cynical as quotes go, but I think the deeper message is important- that of realising that your parents are human and imperfect just like everyone else, rather than the absolute bastion of law and truth that they were when you were a child.
In my experience, some people don't seem to make it past the first stage, and that can be very difficult to deal with when it becomes a case of "me or them".
This sounds like the old "it's not you it's me" line. On the surface it comes from a place of care because she doesn't want to risk your life, but phrasing things like that can end up being quite hurtful and selfish as it pins the blame squarely on you for simply existing, while giving you no way to actually fix the problem.
And if she claims to not believe, then there should be no risk to begin with. If she's still unwilling to move forward given that, then it sounds like either a case of the superstition being stronger than she's willing to admit, or the parents running her life.
For what it's worth I think you went the right way. I had a sort of similar (life choice/family breaking up an otherwise great relationship) thing happen to me some years ago and - while it feels like your world has suddenly gone from coupled bliss to a schadenfreude comedy with you in the starring role - stepping back, accepting that the other person has made their choice, and getting on with your life is so much more healthy than keeping yourself eyes-deep in the situation clinging to the notion that there's some tiny chance that things will work out. Better to carpe diem and keep going.
Sorry to drivel on, but sometimes things pop into a man's head that just need to be put to text- this thread has been quite the thought provoker. Hope my rambling is helpful in some way, keep your head high OP