Destroy is the only canon ending considering the point of Mass Effect's story is to destroy the reapers and the other endings are a slap in its face.
If you want to get technical, the "indoctrination" fan theory is much more compelling and better constructed than the real endings that I'm willing to believe Sheppard never leaves London, everything from there on is a hallucination where he is tested one final time by the Reapers and anything except Destroy is the Reapers finally taking control of Sheppard while Destroy is Sheppard finally breaking free of their hold.
I understand how much you've accomplished with her throughout the entire Mass Effect franchise, but Shepard was meant for this. Someday Shepard was going to make a big sacrifice in order to protect what he/she was fighting for. Shepard fought so much to protect the galaxy, and now has to answer the ultimate question that will determine the fate of the galaxy.