Oh, neither you nor my little darlings would like to know....
Forcing them to wear the same clothes at school for two days in a row would be just the beginning of their troubles....
But, to be quite serious, I take anything I get from them as an unexpected gift. I have seen it as an absolutely essential task to impregnate them with love of all kinds, because I believe that that is the best protection against all evils that surround them - and yes, there have been and are quite a few. But so far, I detect no falseness in them. Evening prayers, occasional children's classes and Virtues discussions, all based on the Bahá'í conception of the soul as a little seed that needs to be fed and nourished, seem to work - so far. But my main objective has not been to receive love from them, but to fill them with it.
To the heart of the matter, if your intended is a Baha'i, and you simply cannot stomach the Baha'i wedding ceremony, why not tell her so? There is no point in not being direct about it. Her faith is going to be very important to her. She's made commitments to it not easily broken, and you would probably not value her as much if she did.
No message forum will help you in this regard. If you were wanting, for instance, to become a Freemason, but your deep convictions as an atheist prevented you from taking certain oaths, then no amount of arguing or debating the point on a message forum of Freemasons would assist you.
I had similar problems with the line, until I realized I didn't have to mean it- at least not in the same sense that the line was literally about. Sure, the line itself is just a required statement for me and doesn't carry any meaning for me, but if I feel in my heart like I'm saying something like "Verily I will be true to her" or "I do" when I'm saying it, then it doesn't feel dishonest.
I think you're right that you need to be able to find a way to be able to say this line and sincerely mean it. You've found a way which works for you.
Here's something that occurs to me though. Baha'u'llah said that God is an unknowable Essence. Nobody knows God directly, but God is manifested or reflected throughout all of creation and especially in a human heart that is pure. I'm guessing that one of the things you love most of all about your girlfriend is the divine you see reflected in her. But it's also in you and there's the attraction.
But people can also be quite ungodly when they get caught up with following their egos. Shoghi Effendi said:
".. Self has really two meanings, or is used in two senses, in the Bahá'í writings: one is self, the identity of the individual created by God. This is the self mentioned in such passages as 'he hath known God who hath known himself etc.'. The other self is the ego, the dark, animalistic heritage each one of us has, the lower nature that can develop into a monster of selfishness, brutality, lust and so on. It is this self we must struggle against, or this side of our natures, in order to strengthen and free the spirit within us and help it to attain perfection...
So maybe abiding by the will of God could be translated as striving to develop your higher nature and help your future wife and children to do the same. I believe this is the will of God. That we all learn to mirror forth divine attributes, not that we all call ourselves Baha'is, Christians, Hindus or whatever.
Unfortunately it seems the most likely outcome was that he did tell her, and that it broke them apart. And I hope he didn't kill himself, but his relationship with her might have been his support system and the fact that that ended could have sent him off the cliff so to speak.
If he couldn't stand on his own and was going to kill himself because of losing her then he was probably not a very good candidate for a peaceful, loving marriage anyway. Not very stable. My daughter once had a boyfriend who said that if she left him he would kill himself. She was kind-hearted and stayed with him much longer than was wise just because of her fears for his well-being, but it ended up making her so unhappy, which, of course made him unhappy, that she finally had to break up anyway. He never killed himself though and within a short time he had found someone new.
Choosing a partner for life is a heavy decision, and divorces are so common. People need to feel free to use any criteria they feel is important to them (including and perhaps especially what their Faith says) rather than stifling their own personal concerns out of fear that their partner will hurt themselves if they don't marry them.