At risk of boring people with my Existentialism, it comes back to the old question, "what is necessary here?"
If you put off resolving this you will both suffer more, so it is always better to act as soon as a problem becomes apparent.
If, after you have talked things through really thoroughly, and I mean totally, you can't see any way to stay together, then parting is the only option. Better to part as friends in tears, rather than growing to resent and hate each other.
You may end up as best friends, almost sisters, as your transition progresses and that is worth a lot.
It's a hard choice, but ultimately better than a life-time self-evasion, deception and resentment.
Karen.