Understand your feelings totally. In fact, this type of conundrum comes up fairly often and you can find some discussion on it here in a couple places.
I think you'll discover that the general consensus is that each situation has to proceed in it's own unique way.
You expressed your understanding of the reality of the situation and that BECAUSE you care you would never want to damage your GF's relationship with her family because of your own desires. I agree - that would just be quite selfish - not a prime example of loving - right?
So often we run into situations where the state of the world conflicts with our own internal compass. We often have to revert back into a damage control mode. How do we maximize the benefit and minimize the harm ?
But I do like what Stitchwitch said about the shifting sands of time (and opinion). I hope you can take some comfort in the fact that although things may be what they are right now, it may not always be that way.
The old saying...."patience is a virtue"